_Fossil Fishes._--Fishes have existed fr_The Geographical Distribution of Animals, Volume 2 With a study of the relations of living and extinct faunas as elucidating the past changes of the Earth's surface

remarkable that the first whose remains have been {467}discovered belong to

the Ganoidei, a highly developed group which has continued to exist down to

our times, and of which the sturgeon is the best known example. We may

therefore be sure that the Upper Silurian rocks in which these are found,

although so very far back in geological history, do not by any means lead

us to the time when the primitive fish-type appeared upon the earth. In the

Carboniferous and Permian formations numerous remains of fishes are found,

allied to the _Lepidosteus_ or Gar-pike of North America. The next group in

order of appearance, are the Plagiostomata, containing the existing Sharks

and Rays. Traces of these are found in the highest Silurian beds, and

become plentiful in the Devonian and Carboniferous formations and in all

succeeding ages, being especially abundant in Cretaceous and Eocene strata.

The Holocephali appear first in the Oolitic period, and are represented by

the living Chimæridæ. The Dipnoi, to which belong the _Lepidosiren_ and

_Ceratodus_, are believed to have existed in the Triassic period, from the

evidence of teeth almost identical with those of the existing Australian

fish. All the ancient fossil fishes belong to the above-mentioned groups,

and many of them have little resemblance to existing forms. The Teleostean

fishes, which form the great bulk of those now living, cannot be traced

back further than the Cretaceous period, while by far the larger number

first appear in the Tertiary beds. The Salmonidæ, Scopelidæ, Percidæ,

Clupeidæ, Scombresocidæ, Mugilidæ, and Siluridæ, or forms closely allied to

them, are found in the Cretaceous formation. In the Eocene beds we first

meet with Squammipennes, Cyprinidæ, Pleuronectidæ, Characinidæ, Murænidæ,

Gadidæ, Pediculati, Syngnathidæ, and Hippocampidæ.

Most of these fossils represent marine fishes, those of fresh-water origin

being rare, and of little importance as an aid in determining the causes of

the distribution of living forms. To understand this we must look to the

various changes of the land surface which have led to the existing

distribution of all the higher vertebrates, and to those special means of

dispersal which Mr. Darwin has shown to be possessed by all fresh-water

productions.

{468}CHAPTER XXI.

THE DISTRIBUTION OF SOME OF THE MORE IMPORTANT FAMILIES AND GENERA OF

INSECTS.

Although insects are, for the most part, truly terrestrial animals, and

illustrate in a very striking manner the characteristic phenomena of

distribution, it is impossible here to treat of them in much detail. This

arises chiefly from their excessive numbers, but also from the minuteness

and obscurity of many of the groups, and our imperfect knowledge of all but

the European species. The number of described species of insects is

uncertain, as no complete enumeration of them has ever been made; but it

probably exceeds 100,000, and these may belong to somewhere about 10,000

genera--many times more than all vertebrate animals together. Of the eight

Orders into which Insects are usually divided, only two--the Coleoptera and

Lepidoptera--have been so thoroughly collected in all parts of the globe

that they can be used, with any safety, to compare their distribution with

that of vertebrate animals; and even of these it is only certain favourite

groups which have been so collected. Among Lepidoptera, for example,

although the extensive group of Butterflies may be said, in a general

sense, to be thoroughly well known--every spot visited by civilized man

having furnished its quota to our collections--yet the minute Tineidæ, or

even the larger but obscure Noctuidæ, have scarcely been collected at all

in tropical countries, and any attempt to study their geographical

distribution would certainly lead to erroneous results. The same thing

occurs, though perhaps in a less degree, among the Coleoptera. While the

Carabidæ, Buprestidæ, and {469}Longicorns of the Tropics, are almost as

well known as those of the Temperate Zones, the Staphylinidæ, the smaller

Elateridæ, and many other obscure and minute groups, are very imperfectly

represented from extra-European countries. I therefore propose to examine

with some care the distribution of the Butterflies, and the Sphingina among

Lepidoptera, and the following large and well-known families of

Coleoptera:--Cicindelidæ, Carabidæ, Lucanidæ, Cetoniidæ, Buprestidæ, and

the three families of Longicorns. These families together contain over

30,000 species, classed in nearly 3,000 genera, and comprise a large

proportion of the best known and most carefully studied groups. We may

therefore consider, that a detailed examination of their distribution will

lead us to results which cannot be invalidated by any number of isolated

facts drawn from the less known members of the class.

_Range of Insects in Time._--In considering how much weight is to be given

to facts in insect distribution, and what interpretation is to be put upon

the anomalies or exceptional cases that may be met with, it is important to

have some idea of the antiquity of the existing groups, and of the rate at

which the forms of insect life have undergone modification. The geological

record, if imperfect in the case of the higher animals, is fragmentary in

the extreme as regards indications of former insect life; yet the positive

facts that it does disclose are of great interest, and have an important

bearing on our subject. These facts and the conclusions they lead to have

been discussed in our first volume (p. 166), and they must be carefully

weighed in all cases of apparent conflict or incongruity between the

distribution of insects and that of the higher animals.

{470}_Order--LEPIDOPTERA._

Sub-order--_Lepidoptera_ RHOPALOCERA, or BUTTERFLIES.

FAMILY 1.--DANAIDÆ. (24 Genera, 530 Species.)

GENERAL DISTRIBUTION.

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The Danaidæ are now held to comprehend, not only the whole of the group so

named by Doubleday, but a large portion of the Heliconidæ of that author.

Their range is thus extended over the whole of the tropical regions. A few

species spread northwards into the Palæarctic and Nearctic regions, but

these are only stragglers, and hardly diminish the exclusively tropical

character of the group. The more remarkable genera are,--_Hestia_ (10 sp.),

and _Ideopsis_ (6 sp.), confined to the Malayan and Moluccan districts;

_Danais_ (50 sp.), which has the range of the whole family; _Euploea_ (140

sp.), confined to the Oriental and Australian regions, but especially

abundant in the Malayan and Moluccan districts; _Hamadryas_ (4 sp.),

Australian region only. The remaining genera constitute the Danaioid

Heliconidæ, and are strictly confined to Tropical America, except a few

species which extend into the southern parts of the Nearctic region. The

chief of these genera are:--

_Ithomia_ (160 sp.), _Melinæa_ (18 sp.), _Napeogenes_ (20 sp.),

_Mechanitis_ (4 sp.), _Ceratina_ (32 sp.), _Dircenna_ (10 sp.), and

_Lycorea_ (4 sp.). Florida, Louisiana, and Southern California, mark the

northern extent of these insects.

{471}FAMILY 2.--SATYRIDÆ. (60 Genera, 835 Species.)

GENERAL DISTRIBUTION.

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This family has an absolutely universal distribution, extending even into

the Arctic and Antarctic regions. Many of the genera are, however,

restricted in their range.

_Hætera_, _Lymanopoda_, _Calisto_, _Corades_, _Taygetis_, _Pronophila_,

_Euptychia_, and some allied forms (25 genera in all) are Neotropical, the

last named extending north to Canada; _Debis_, _Melanitis_, _Mycalesis_ and

_Ypthima_, are mostly Oriental, but extending also into the Australian and

the Ethiopian regions; _Gnaphodes_, _Leptoneura_, and a few other small

genera, are exclusively Ethiopian; _Xenica_, _Hypocista_, and

_Heteronympha_, are Australian; _Erebia_, _Satyrus_, _Hipparchia_,

_Coenonympha_, and allies, are mostly Palæarctic, but some species are

Ethiopian, and others Nearctic; _Chionabas_, is characteristic of the whole

Arctic regions, but is also found in Chili and the Western Himalayas. The

peculiar genera in each region are,--Neotropical, 25; Australian, 7;

Oriental, 11; Ethiopian, 5; Palæarctic, 3; Nearctic, 0.

FAMILY 3.--ELYMNIIDÆ. (1 Genus, 28 Species.)

GENERAL DISTRIBUTION.

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The genus _Elymnias_, which constitutes this family, is characteristic of

the Malayan and Moluccan districts, with some species in Northern India and

one in Ashanti. It thus agrees with several groups of Vertebrata, in

showing the resemblance {472}of Malaya with West Africa independently of

the Peninsula of India.

FAMILY 4. MORPHIDÆ. (10 Genera, 106 Species.)

GENERAL DISTRIBUTION.

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The Morphidæ are a group of generally large-sized butterflies, especially

characteristic of the Malayan and Moluccan districts, and of Tropical

America; with a few species extending to the Himalayas on the west, and to

Polynesia on the east. The genera are:--

_Amathusia_ (6 sp.), Northern India to Java; _Zeuxidia_ (9 sp.), the Malay

district; _Discophora_ (7 sp.), Northern India to Philippines, Java and

Timor; _Enispe_ (3 sp.), Northern India; _Hyades_ (15 sp.), Moluccan and

Polynesian districts, except one species in Java; _Clerome_ (11 sp.),

Northern India to Philippines and Celebes; _Æmona_ (1 sp.), Sikhim;

_Hyantis_ (1 sp.), Waigiou; _Thaumantis_ (10 sp.), Indo-Chinese and Malayan

districts; _Morpho_ (40 sp.), Neotropical region, Brazilian and Central

American sub-regions.

FAMILY 5. BRASSOLIDÆ. (7 Genera, 62 Species.)

GENERAL DISTRIBUTION.

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The Brassolidæ have the same distribution as the genus _Morpho_. The genera

are:--

_Brassolis_ (5 sp.); _Opsiphanes_ (17 sp.); _Dynastor_ (2 sp.); _Penetes_

(1 sp.); _Caligo_ (21 sp.); _Narope_ (5 sp.); and _Dasyopthalma_ (3 sp.)

{473}FAMILY 6.--ACRÆIDÆ. (1 Genus, 90 Species.)

GENERAL DISTRIBUTION.

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The genus _Acræa_ is especially abundant in the Ethiopian region, which

contains two-thirds of all the known species; 3 or 4 species only, range

over the whole Oriental, and most of the Australian regions; while all the

rest inhabit the same districts of the Neotropical region as the

Brassolidæ.

FAMILY 7.--HELICONIDÆ. (2 Genera, 114 Species.)

GENERAL DISTRIBUTION.

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The true Heliconidæ are very characteristic of the Neotropical region; one

species only extending into the Southern States of North America as far as

Florida. The genus _Heliconius_ (83 sp.), has the range of the family;

while _Eueides_ (19 sp.), is confined to the Brazilian and Central American

sub-regions.

FAMILY 8.--NYMPHALIDÆ. (113 Genera, 1490 Species.)

GENERAL DISTRIBUTION.

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This is the largest and most universally distributed family of butterflies,

and is well illustrated by our common Fritillaries, {474}Tortoise-shell,

Peacock, Painted Lady, and Purple Emperor butterflies. They are found

wherever butterfly-life can exist, and some single species--like the

Painted Lady (_Pyrameis cardui_)--range almost over the globe. A few of the

more extensive and remarkable genera only, can be here noticed:--

_Colænis_, _Agraulis_, _Eresia_, _Synchloe_, _Epicalia_, _Eunica_,

_Eubagis_, _Catagramma_, _Callithea_, _Ageronia_, _Timetes_, _Heterochroa_,

_Prepona_, _Hypna_, _Paphia_, and _Siderone_, are wholly Neotropical, as

well as many others which have a smaller number of species. _Euryphene_,

_Romaleosoma_, _Aterica_, and _Harma_, are exclusively Ethiopian.

_Terinos_, _Athyma_, _Adolias_, and _Tanæcia_, are Oriental, but they

mostly extend into the Moluccan region; the last however is strictly

Malayan, and _Adolias_ only reaches Celebes. _Mynes_ alone, is exclusively

Australian, but _Prothoe_ is almost so, having only one outlying species in

Java. _Eurytela_ and _Ergolis_ are confined to the Oriental and Ethiopian

regions, but the latter reaches the Moluccas. _Cethosia_, _Cirrhochroa_,

_Messaras_, and _Symphædra_, are both Oriental and Australian; while

_Junonia_, _Cyrestis_, _Diadema_, _Neptis_, and _Nymphalis_, are common to

the three tropical regions of the Eastern Hemisphere, the latter extending

into the Mediterranean district, while _Junonia_ occurs also in South

America and the Southern United States.

The most cosmopolitan genus is _Pyrameis_, which has representatives in

every region and every district. _Apatura_ is found in all but the

Ethiopian and the Australian, although it just enters the confines of the

latter region in Celebes; _Limenitis_ is abundant in the Oriental region,

but extends eastward to Celebes and westward into Europe, North America,

and even into South America. _Argynnis_, _Melitæa_, and _Vanessa_, are

almost confined to the Palæarctic and Nearctic regions; the former however

occurs in the Himalayas and in the mountains of Java, and also in Chili and

in Jamaica. Two genera--_Dicrorrhagia_ and _Helcyra_--have both one species

in North India and another in the island of Ceram. The number of genera

peculiar to each region is as follows:--Neotropical, 50; Australian, 2;

Oriental 15; Ethiopian, 14; Palæarctic, 1; Nearctic, 0.

{475}FAMILY 9.--LIBYTHEIDÆ. (1 Genus, 10 Species.)

GENERAL DISTRIBUTION.

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The genus _Libythea_, which constitutes this family, appears to have its

head-quarters in the Oriental region, but extends on all sides in an

erratic manner, into various remote and disconnected portions of the globe,

as indicated above.

FAMILY 10.--NEMEOBIIDÆ. (12 Genera, 145 Species.)

GENERAL DISTRIBUTION.

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This group has been separated from the Erycinidæ of the older authors, and

contains all the non-American genera and species. Half the genera and

nearly four-fifths of the species of this group are, however, Neotropical;

one is European; two or three African; and twenty-six Oriental and

Australian. The genera are:--

_Nemeobius_ (1 sp.), Europe; _Dodona_ (6 sp.), North India; _Zemeros_ (2

sp.), North India and Malaya; _Abisara_ (11 sp.), North India, Malayan and

Moluccan districts, Madagascar and West Africa; _Taxila_ (8 sp.), North

India and Malaya; _Dicallaneura_ (2 sp.), Moluccan district; _Alesa_ (6

sp.), _Eunogyra_ (2 sp.), _Cremna_ (7 sp.), _Bæotis_ (3 sp.), are all from

the Brazilian sub-region; _Eurybia_ (10 sp.), _Mesosemia_ (80 sp.), inhabit

both the Brazilian and Mexican sub-regions.

{476}FAMILY 11.--EURYGONIDÆ. (2 Genera, 78 Species.)

GENERAL DISTRIBUTION.

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This small family, separated from the true Erycinidæ by Mr. Bates, is

confined to the tropical forest-districts of continental America. The

genera are:--

_Eurygona_ (71 sp.); _Methonella_ (1 sp.); the latter found in Equatorial

South America.

FAMILY 12.--ERYCINIDÆ. (59 Genera, 560 Species.)

GENERAL DISTRIBUTION.

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This extensive family of small, but exquisitely beautiful butterflies, is

especially characteristic of the virgin forests of the Neotropical region,

only a few species of three genera extending into the Nearctic region. The

more important genera, and those which have an exceptional distribution,

can alone be here noticed. _Charis_ extends from Brazil to New York;

_Apodemia_ from Brazil to California, Utah, and Oregon; _Amarynthis_

inhabits the Brazilian and Antillean sub-regions; _Lepricornis_ and

_Metapheles_ are small genera found only in the Mexican sub-region;

_Lymnas_, _Necyria_, _Ancyluris_, _Diorhina_, _Esthemopsis_, _Anteros_,

_Emesis_, _Symmachia_, _Cricosoma_, _Calydna_, _Lemonias_, _Nymphidium_,

_Theope_, and _Aricoris_ are common to the Brazilian and Mexican

sub-regions. All the other genera (40 in number) are only known from the

Brazilian sub-region, and of these a considerable proportion are confined

to the damp equatorial forests of the Amazon Valley.

{477}FAMILY 13.--LYCÆNIDÆ. (39 Genera, 1,220 Species.)

GENERAL DISTRIBUTION.

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The Lycænidæ--of the variety and beauty of which in tropical regions our

own "Blues" and "Coppers" give but a faint idea--are a group of universal

distribution. We shall therefore indicate those genera which are restricted

to one or more regions, or are nearly cosmopolitan. The large genus

_Polyommatus_ (containing 325 species) has the same universal distribution

as the entire family. Our common "Blues" well represent this genus.

_Lycæna_ (comprising the "Coppers") is more especially characteristic of

the Palæarctic and Nearctic regions, but straggling species occur also in

North India, South Africa, Chili, and New Zealand. _Thecla_ is especially

characteristic of the Neotropical region, where there are about 370

species; in the Nearctic region, 36; in the Palæarctic 13; and in the

Ethiopian 3. _Miletus_, _Lucia_, _Hypolycæna_, _Myrina_, and _Deudorix_ are

common to the three tropical regions of the Eastern Hemisphere--the

Ethiopian, Oriental, and Australian. _Aphneus_ and _Iolaus_ are common to

the Ethiopian and Oriental regions, the latter extending to Celebes.

_Ialmenus_, _Pseudodipsas_, _Curetis_, and _Amblypodia_ are common to the

Oriental and Australian regions, but the first-named is found also in

Madagascar. _Zephyrus_ is found only in the Nearctic and Palæarctic,

_Eumæus_ in the Nearctic and Neotropical regions. The Nearctic region has

one peculiar genus (_Feniseca_); the Palæarctic has two--_Thestor_ and

_Læosopis_; the Ethiopian has nine--_Pentila_, _Liptana_, _D'Urbania_,

_Axiocerces_, _Capys_, _Phytala_, _Epitola_, _Hewitsonia_, and _Deloneura_;

the Oriental has five--_Allotinus_, _Ilerda_, _Poritia_, _Camena_, and

_Liphyra_; the Australian has three--_Hypochrysops_, _Utica_, and _Ogyris_;

and the Neotropical also three--_Lamprospilus_, _Theorema_, and

_Trichonis_.

{478}FAMILY 14.--PIERIDÆ. (35 Genera, 817 Species.)

GENERAL DISTRIBUTION.

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The Pieridæ are distributed almost, if not quite, as widely over the globe

as the last family, and we shall group the genera in the same manner.

_Pieris_ (130 sp.) is cosmopolitan; _Terias_ and _Callidryas_ are found in

all the four tropical regions, and as far north as Pennsylvania in the

Nearctic region; _Pontia_, _Tachyris_, _Eronia_, and _Thestias_ are common

to the Ethiopian, Oriental, and Australian regions, the last-named,

however, only extending as far as Timor; _Colias_ is pre-eminently

Palæarctic and Nearctic, with a few Ethiopian species, one Indian, two in

Chili, and one in the Sandwich Islands; _Anthocharis_ is wholly Palæarctic

and Nearctic; _Midea_ has two species Nearctic, and one in Japan;

_Gonepteryx_ is Palæarctic and Neotropical, extending into Texas; _Idmais_

and _Callosune_ are Ethiopian and Oriental; _Thyca_ and _Iphias_ are

Oriental and Australian; _Meganostoma_ is Nearctic and Neotropical;

_Nathalis_ and _Kricogonia_ are Neotropical, ranging into Florida, Texas,

and Colorado.

The peculiar genera are pretty equally distributed. The Neotropical region

has ten, two being confined to Chili; _Euterpe_ and _Leptalis_ are the most

remarkable, the latter containing a number of forms mimicking the

Heliconidæ and Danaidæ. The Oriental region has two, _Prioneris_ and

_Dercas_, the Australian one, _Elodina_; the Ethiopian two, _Teracolus_ and

_Pseudopontia_; the Palæarctic two, _Leucophasia_ and _Zegris_; the

Nearctic one, _Neophasia_.

{479}FAMILY 15.--PAPILIONIDÆ. (13 Genera, 455 Species.)

GENERAL DISTRIBUTION.

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The Papilionidæ, comprising many of the noblest and richest-coloured

butterflies, and long placed at the head of the group, are almost as

universally distributed as the Pieridæ, but they do not extend to so many

remote islands nor so far into the Arctic and Antarctic regions.

Nine-tenths of the species belong to the genus _Papilio_, and these are

especially abundant in tropical regions, although species occur in every

region and every sub-region. Well-marked sub-divisions of this large genus

are characteristic of each great region--as the "Æneas" group in the

Neotropical, the "Paris" group in the Oriental, the "Ægeus" group in the

Australian, the "Zenobius" group in the Ethiopian, and many others. The few

species of the Palæarctic region belong, on the other hand, to a group of

universal distribution, and the Nearctic has a good number of species

allied to Neotropical forms.

The other genera have mostly a very restricted range. _Parnassius_ is an

Alpine genus, confined to the Palæarctic and Nearctic regions. The

Palæarctic region further possesses 5 peculiar genera--_Mesapia_,

_Hypermnestra_, _Doritis_, _Sericinus_, and _Thais_; the Oriental has 4,

_Calinaga_, _Teinopalpus_, _Bhutanitis_, and _Leptocircus_, the latter

going as far as Celebes; the Australian has 1, _Eurycus_; and the

Neotropical 1, _Euryades_, confined to the Chilian sub-region. The

Ethiopian and the Nearctic regions have no peculiar genera.

{480}FAMILY 16.--HESPERIDÆ. (52 Genera (?), 1,200 Species.)

GENERAL DISTRIBUTION.

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The Hesperidæ, or Skippers, are an immense group of mostly small obscurely

coloured butterflies, universally distributed, and of which hosts of

species still remain to be discovered and described. As the grouping of

these into genera is not yet satisfactorily accomplished, only the more

extensive and best known groups will be here noticed. _Pamphila_ and

_Hesperia_ are universally distributed; _Nisoniades_ seems to be only

absent from the Australian region. The Neotropical region is pre-eminently

rich in Hesperidæ, 33 genera being found there, of which 20 are peculiar to

it; the Australian region has 12 genera, only 1 (_Euschemon_) being

peculiar; the Oriental has 18, with 3 peculiar; the Ethiopian, 13, with 3

peculiar; the Palæarctic 6, with 1 (_Erynnis_) almost peculiar, a species

occurring in Mexico; the Nearctic 9, with none peculiar, 4 being found also

in the Neotropical region, 2 in the Palæarctic, and the rest being of wide

distribution. Many new genera have, however, been recently described in the

United States, but it is impossible yet to determine how many, if any, of

these are peculiar. More than 100 species of the family are included in Mr.

Edwards' "Synopsis of North American Butterflies,"--a very large number

considering that Europe possesses only about 30.

{481}Sub-order--LEPIDOPTERA HETEROCERA, or MOTHS.

The Lepidoptera Heterocera, or Moths, are of such immense extent, and are,

besides, so imperfectly known compared with the Butterflies, that it would

serve no purpose to go into the details of their distribution; especially

as most of the families and a considerable number of the genera are

cosmopolitan. We propose therefore to notice only the Sphingina, which,

being generally of large size and finely marked or coloured, and many of

them day-fliers, have been extensively collected; and whose numbers are

more manageable than the succeeding groups.

_Group I.--SPHINGINA._

FAMILY 17.--ZYGÆNIDÆ (46 Genera, about 530 Species).

The Zygænidæ are universally distributed, but many of the genera are

restricted in their range. _Zygæna_ (85 sp.) is mainly Palæarctic, but 2

species are South African, and 1 North American; _Procris_ (22 sp.) has a

scattered distribution, from the Palæarctic region to South America, South

Africa and North India; _Heterogynis_ (3 sp.) and _Dysauxis_ (3 sp.) are

European; _Pollanisus_ (3 sp.) is Australian; _Glaucopis_ (120 sp.) is

mainly Neotropical, with a few Oriental; _Syntomis_ (94 sp.) is found in

all the Old-World regions; and _Euchromia_ (150 sp.) is found in all warm

countries, though especially abundant in South America.

FAMILY 18.--CASTNIIDÆ (7 Genera, 63 Species).

The Castniidæ have an interesting distribution, being mainly Neotropical,

with four genera in Australia and New Guinea. _Castnia_, _Coronis_, and

_Gazera_, with 51 species, are Neotropical; _Synemon_, _Euschemon_,

_Damias_ and _Cocytia_, with 12 species, are Australian, the latter being

found only in the Papuan Islands.

{482}FAMILY 19.--AGARISTIDÆ (13 Genera, 76 Species).

The Agaristidæ are beautiful diurnal moths, allied to the Castniidæ, but

almost confined to the Australian and Oriental regions, with a few in the

Ethiopian. The most important genera are,--_Agarista_ (21 sp.), Australia

and New Guinea; _Eusemia_ (31 sp.), _Ægocera_ (7 sp.), Oriental and

Ethiopian regions; the other genera being confined to the islands from Java

to New Guinea.

FAMILY 20.--URANIIDÆ (2 Genera, 12 Species).

These magnificent insects have a singular distribution. The gold-spangled

_Urania_ (6 sp.) is characteristic of Tropical America, but a single

species of great magnificence occurs in Madagascar. The large but

sober-tinted _Nyctalemon_ (6 sp.) is found in the Neotropical, Oriental,

and Australian regions.

FAMILY 21.--STYGIIDÆ. (3 Genera, 14 Species.)

These insects are confined to the Palæarctic and Neotropical regions, 2

genera in the former, 1 in the latter.

FAMILY 22.--ÆGERIIDÆ. (24 Genera, 215 Species.)

This family is found in all parts of the world except Australia. _Ægeria_

is most abundant in Europe, but is found also in North and South America.

FAMILY 23.--SPHINGIDÆ. (40 Genera, 345 Species.)

The Sphinx Moths are cosmopolitan. The most important genera

are,--_Macroglossa_ (26 sp.), _Chærocampa_ (46 sp.), and _Macrosila_ (21

sp.), all cosmopolitan; _Sesia_ (12 sp.), Europe, Asia, and North America;

_Deilephila_ (19 sp.), Palæarctic and Oriental regions, Nearctic region,

and Chili; _Sphinx_ (21 sp.), Europe, {483}North and South America;

_Smerinthus_ (29 sp.), all regions except Australia. Our Death's Head Moth

(_Acherontia atropos_) ranges to Sierra Leone and the Philippine Islands.

_General Remarks on the Distribution of the Diurnal Lepidoptera and

Sphingidea._

The Diurnal Lepidoptera or Butterflies, comprehend 431 genera and 7,740

species, arranged in 16 families, according to Mr. Kirby's Catalogue

published in 1871. The Sphingidea consist of 135 genera and 1,255 species,

arranged in 7 families, according to the British Museum Catalogue dated

1864; and as this includes all Mr. Bates' collections in America and my own

in the East, it is probable that no very large additions have since been

made.

The distribution of the families and genera of Butterflies corresponds

generally with that of Birds--and more especially with that of the

Passerine birds--in showing a primary division of the earth into Eastern

and Western, rather than into Northern and Southern lands. The Neotropical

region is by far the richest and most peculiar. It possesses 15 families of

butterflies, whereas the other regions have only from 8, in the Palæarctic,

to 12 in the Ethiopian and Oriental regions; and as none of the Old World

regions possess any peculiar families, the New World has a very clear

superiority. In genera the preponderance is still greater, since the

Neotropical region possesses about 200 altogether peculiar to it, out of a

total of 431 genera, many of which are cosmopolitan. Comparing, now, the

Eastern regions with the Western, we have two peculiar families in the

former to 4 in the latter; while the Southern regions (Australian and

Neotropical) possess not a single peculiar family in common.

In the Sphingidea the same general features recur in a less marked degree,

the Neotropical being the richest region; but here we have one family

(Castniidæ) which appears to be confined to the two southern regions,--the

Australian and Neotropical.

The distribution of the genera affords us some facts of special interest,

which must be briefly noticed. There are several {484}genera typically

characteristic of the North Temperate regions which have a few species

widely scattered on mountains, or in the temperate parts of the Southern

Hemisphere. Chili possesses representatives of four of these

genera--_Argynnis_, _Lycæna_, _Colias_, and _Deilephila_; and this has been

thought by some naturalists to be of such importance as to outweigh the

purely Neotropical character of a large portion of the Chilian fauna, and

to render it advisable to join it on, as an outlying portion of a great

North Temperate zoological region. But when we remember that _Argynnis_

occurs also in Java, and _Lycæna_ in New Zealand, while _Colias_ ranges to

Southern Africa, Malabar, and the Sandwich Islands, we can hardly admit the

argument to be a sound one. For a fuller discussion of this question see

Vol. II., pp. 43-47. The remarkable fact of the existence of the otherwise

purely Neotropical genus, _Urania_, in Madagascar is even more striking,

supported as it is by the Antillean, _Solenedon_, belonging to a family of

Mammalia otherwise confined to Madagascar, and by one or two Coleopterous

genera, to be noticed farther on as common to the two countries. Our view

as to the true explanation of this and analogous phenomena will be found at

Vol. I., p. 284.

The division of the Castniidæ (a family almost confined to the Tropics),

between the Neotropical and Australian regions, is also a very curious and

important phenomenon, because it seems to point to a more remote connection

between the two countries than that indicated by the resemblance between

the productions of South Temperate America with those of Australia and New

Zealand; but we have already shown that the facts may be explained in

another way. (See Vol. I., pp. 398 and 404).

The division of the Malay Archipelago between the Oriental and Australian

regions is clearly marked in the Lepidoptera, and it is very curious that

it should be so, for in this, if in any group of animals, we should expect

an almost complete fusion to have been effected. Lepidoptera fly readily

across wide tracts of sea, and there is absolutely no climatal difference

to interfere with their free migration from island to island. Yet we find

no less than 10 genera abundant in the Indo-Malayan {485}sub-region which

never cross the narrow seas to the east of them; 6 others which only pass

to Celebes; and 2 more which have extended from Java along the closely

connected line of islands eastwards to Timor. On the other side, we find 5

strictly Austro-Malayan genera, and 2 others which have a single

representative in Java. The following is a list of these genera:--

INDO-MALAYAN GENERA:--_Amathusia_, _Thaumantis_, _Tanæcia_, _Eurytela_,

_Ilerda_, _Zemeros_, _Taxila_, _Aphneus_, _Prioneris_, _Dercas_, _Clerome_,

_Adolias_, _Apatura_, _Limenitis_, _Iolaus_, _Leptocircus_, (the last six

reach Celebes); _Discophora_, _Thestias_; (the last two reach Timor.)

AUSTRO-MALAYAN GENERA:--_Hamadryas_, _Hypocista_, _Mynes_, _Dicallaneura_,

_Elodina_, _Hyades_, _Prothoë_ (the last two reach Java).

The most characteristic groups, which range over the whole Archipelago and

give it a homogeneous character, are the various genera of Danaidæ, the

genus _Elymnias_, and _Amblypodia_ with a few other Lycænidæ. These are all

abundant and conspicuous groups, but they are nevertheless exceptions to

the general rule of limitation to one or other of the regions. The cause of

this phenomenon is probably to be found in the limitation of the larvæ of

many Lepidoptera to definite species, genera, and families of plants; and

we shall perhaps find, when the subject is carefully investigated, that the

groups which range over the whole Archipelago feed on genera of plants

which have an equally wide range, while those which are limited to one

region or the other, have food-plants belonging to genera which are

similarly limited. It is known that the vegetation of the two regions

differs largely in a botanical sense, although its general aspect is almost

identical; and this may be the reason why the proportion of wide-ranging

genera is greater among such insects as feed upon dead wood, than among

those which derive their support from the juices of the living foliage.

This subject will be again discussed under the various families of

Coleoptera, and it will be well to bear in mind the striking facts of

generic limitation which have been here brought forward.

{486}Fossil Butterflies, apparently of existing genera, occur in the

Miocene and Eocene formations, and an extinct form in the Lower Oolite; but

these cannot be held to give any adequate idea of the antiquity of so

highly specialised a group, which, in all probability, dates back to

Palæozoic times, since one of the Bombycidæ,--a group almost as

highly-organised--has been discovered in the coal formation of Belgium.

(See Vol. I. p. 168.)

_Order--COLEOPTERA._

GEODEPHAGA, or CARNIVOROUS GROUND BEETLES.

The Geodephaga consist of two families, Cicindelidæ and Carabidæ, differing

in their form and habits no less than in their numbers and distribution.

The former, comprising about 800 species, are far more abundant and varied

in Tropical regions; the latter, more than ten times as numerous, are

highly characteristic of the North Temperate zone, where fully half of all

the known species occur.

CICINDELIDÆ. (35 Genera, 803 Species.)

The Cicindelidæ, or Tiger Beetles, are a moderately extensive group, spread

over the whole globe, but much more abundant in tropical than in temperate

or cold countries. More than half of the species (418) belong to the single

genus _Cicindela_, the only one which is cosmopolitan. The other large

genera are,--_Collyris_ (81 sp.), wholly Oriental; _Odontochila_ (57 sp.),

South American, with species in Java and Celebes; _Tetracha_ (46 sp.),

mostly South American, but with species in South Europe, North America, and

Australia; _Tricondyla_ (31 sp.), characteristic of the Oriental region,

but extending eastward to New Guinea; _Ctenostoma_ (26 sp.), wholly

Neotropical; _Dromica_ (24 sp.), wholly African, south of Lake Ngami and

Mozambique; _Therates_ (18 sp.), wholly Malayan, from Singapore to New

Guinea.

The genera are distributed in the several regions as follows:--the Nearctic

region has 5 genera, 3 of which are peculiar to it; the {487}Palæarctic has

2, but none peculiar; the Ethiopian 13, with 11 peculiar; the Oriental 8,

with 3 peculiar; the Australian 9, with 2 peculiar; and the Neotropical 15,

with 10 peculiar. The connection between South America and Australia is

shown by the latter country possessing 9 species of the characteristic

South American genus _Tetracha_, as well as one of _Megacephala_. The small

number of peculiar genera in the Oriental and Australian regions is partly

owing to the circumstance that two otherwise peculiar Oriental genera have

spread eastward to the Moluccas and New Guinea, a fact to be easily

explained by the great facilities such creatures have for passing narrow

straits, and by the almost identical physical conditions in the Malayan

portion of the two regions. The insects of Indo-Malaya were better adapted

to live in the Austro-Malay Islands than those of Australia itself, and the

latter group of islands have thus acquired an Oriental aspect in their

entomology, though not without indications of the presence of an aboriginal

insect-fauna of a strictly Australian type. The relation of the Australian

and Neotropical regions is exhibited by this family in an unusually

distinct manner. _Tetracha_, a genus which ranges from Mexico to La Plata,

has 9 species in Australia; while _Megacephala_ has 2 American and 1

Australian species. Another curious, and more obscure relation, is that

between the faunas of Tropical America and Tropical Africa. This is also

illustrated by the genus _Megacephala_, which has 4 African species as well

as 2 South American; and we have also the genus _Peridexia_, which has 2

species in South America and 2 in Madagascar.

Several of the sub-regions are also well characterised by peculiar genera;

as _Amblychila_ and _Omus_ confined to California and the Rocky Mountains;

_Manticora_, _Ophryodera_, _Platychile_ and _Dromica_, characteristic of

South Africa; _Megalomma_ and _Pogonostoma_ peculiar to the Mascarene

Islands; and _Caledonica_ to the islands east of New Guinea. The extensive

and elegant genus _Collyris_ is highly characteristic of the Oriental

region, over the whole of which it extends, only just passing the limits

into Celebes and Timor.

The Cicindelidæ, therefore, fully conform to those divisions of {488}the

earth which have been found best to represent the facts of distribution in

the higher animals.

CARABIDÆ. (620 Genera, 8500 Species.)

The enormous extent of this family, necessitates a somewhat general

treatment. It has been very extensively collected, while its classification

has been most carefully worked out, and a detailed exposition of its

geographical distribution by a competent entomologist would be of the

greatest interest. A careful study of Gemminger and Harold's Catalogue,

however, enables me to sketch out the main features of its distribution,

and to detail many of its peculiarities with considerable accuracy.

The Carabidæ are remarkable among insects, and perhaps among all

terrestrial animals, as being a wonderfully numerous, varied, conspicuous,

and beautiful group, which is pre-eminently characteristic of the

Palæarctic region. So strikingly and unmistakably is this the case, that it

must be held completely to justify the keeping that region distinct from

those to which it has at various times been proposed to join it. Although

the Carabidæ are thoroughly well represented by hosts of peculiar genera

and abundant species in every part of the world without exception, yet the

Palæarctic region alone contains fully one-third, or perhaps nearer

two-fifths, of the whole. It may also be said, that the group is a

temperate as compared with a tropical one; so that probably half the

species are to be found in the temperate and cold regions of the globe,

leaving about an equal number in the much more extensive tropical and warm

regions. But, among the cold regions, the Palæarctic is pre-eminent. North

America is also rich, but it contains, by far, fewer genera and fewer

species.

The magnificent genus _Carabus_, with its allies _Procerus_ and

_Procrustes_, containing about 300 species, all of large size, is almost

wholly confined to the Palæarctic region, only 10 species inhabiting North

America, and 11 Temperate South America, with one on the African mountain

of Kilimandjaro. Twelve large genera, containing together more than 2000

species, are truly cosmopolitan, inhabiting both temperate and tropical

{489}countries all over the globe; but many of these are more abundant in

the Palæarctic region than elsewhere. Such are _Scarites_, _Calosoma_,

_Brachinus_, _Cymindis_, _Lebia_, _Chlænius_, _Platynus_, _Harpalus_,

_Bembecidium_, _Pæcilus_, and _Argutor_. Of tropical cosmopolites, or

genera found in all the tropical regions, but not in the temperate zones,

there seem to be only four,--_Catascopus_, _Coptodera_, _Colopodes_, and

_Caasnonia_. _Pheropsophus_ is confined to the tropics of the Old World;

while _Drimostoma_, though widely scattered, is characteristic of the

Southern Hemisphere.

The Palæarctic region has about 50 genera of Carabidæ which are strictly

confined to it, the most important being,--_Leistus_ (30 sp.), _Procerus_

(5 sp.), _Procrustes_, (17 sp.), _Zabrus_ (60 sp.), _Pristonychus_ (42

sp.), and _Ophonus_ (60 sp.); but it possesses a large number in common

with the Nearctic region. The more remarkable of these are,--_Carabus_,

_Nebria_, _Amara_, _Cyrtonotus_, _Bradycellus_, _Anopthalmus_, _Celia_,

_Cychrus_, _Patrobus_, _Elaphrus_, _Notiophilus_, _Bradytus_,

_Callisthenus_, _Blethisa_, and several others. Many too, though not

strictly confined to the North Temperate regions, are very abundant there,

with a few species isolated in remote countries, or widely scattered, often

in an eccentric manner. Among these may be mentioned, _Trechus_ (120 sp.),

all North Temperate but 8, which are scattered in Java, New Caledonia and

South America; _Dyschirus_ (127 sp.), North Temperate, with 3 or 4 species

in Australia, China and La Plata; _Omaseus_, (88 sp.), _Steropus_ (90 sp.),

_Platysoma_ (114 sp.), and _Pterostichus_ (138 sp.), are mostly North

Temperate, but each has a few species in the South Temperate zone, New

Zealand, Australia, Chili, and the Cape of Good Hope. _Dromius_ (54 sp.),

is about two-thirds Palæarctic, the rest of the species being scattered

over the world, in Chili, North and South America, South Africa, Burmah,

Ceylon, and New Zealand. The North Temperate genera _Calathus_ and

_Olisthopus_, have each one species in New Zealand; _Percus_ has most of

its species in South Europe, but 3 in Australia; _Abax_ is confined to the

north temperate zone, but with one species in Madagascar; while

_Læmosthenes_ is said to have a species identically the same in South

Europe and Chili. Some of these apparent anomalies may be due to wrong

{490}determination of the genera, but there can be little doubt that most

of them represent important facts in distribution.

The Nearctic region is comparatively poor in Carabidæ. Its more important

peculiar genera are,--_Dicælus_ (22 sp.), _Pasimachus_ (17 sp.),

_Eurytrichus_ (9 sp.), _Sphæroderus_ (7 sp.), _Pinacodera_ (6 sp.), and

others of smaller extent, about 30 in all. It also possesses

representatives of a considerable number of Palæarctic genera, as already

indicated; and a few of South American genera, of which _Helluomorpha_ and

_Galerita_ are the most important.

The Neotropical region is very rich in peculiar forms of Carabidæ, as in

almost all other great groups. It possesses more than 100 peculiar genera,

but about 30 of these are confined to the South Temperate sub-region. The

more important peculiar genera of Tropical America are,--_Agra_ (144 sp.),

_Ardistomus_ (44 sp.), _Schizogenius_ (25 sp.), _Pelecium_, (24 sp.),

_Calophena_ (22 sp.), _Ctenodactyla_ (7 sp.). Among the Chilian and South

Temperate peculiar forms are,--_Antarctia_ (29 sp.), _Scelodontis_ (10

sp.), _Tropidopterus_ (4 sp.). Among the Neotropical genera with outlying

species are,--_Pachyteles_ (50 sp.), one of which is West African;

_Selenophorus_ (70 sp.), with 4 African, 4 Oriental, and 1 from New

Caledonia; _Ega_ (11 sp), with one in the East Indies, and one in New

Caledonia; _Galerita_, with 36 American species, 8 African, and 3 Indian;

_Callida_ and _Tetragonoderus_, mostly American, but with a few African,

Oriental and Australian species; and _Pseudomorpha_, common to America and

Oceania.

The Australian region is almost equally rich, possessing about 95 peculiar

genera of Carabidæ, no less than 20 of which are confined to New Zealand.

The most important are, _Carenum_, _Promecoderus_, _Scaraphites_,

_Notonomus_, _Ænigma_, _Sphallomorpha_, _Silphomorpha_, and _Adelotopus_.

The gigantic _Catadromus_ has 4 Australian species and 1 in Java;

_Homalosoma_ has 31 species in Australia and New Zealand, and 1 in

Madagascar. Celebes and New Guinea have each peculiar genera, and one is

common to Australia and the Cape of Good Hope.

The Oriental region possesses 80 peculiar genera, 10 of which are confined

to Ceylon. The more important are,--_Pericallus_, _Planetes_, and

_Mormolyce_. _Distrigus_ is also characteristic of this {491}region, with

one species in Madagascar; while it has _Orthogonius_, _Hexagonia_,

_Macrochilus_, and _Thyreopterus_ in common with the Ethiopian region, and

is rich in the fine tropical genus, _Catascopus_.

The Ethiopian region has 75 peculiar genera, 8 of which are confined to

Madagascar. The more important are,--_Polyhirma_, _Graphipterus_, and

_Piezia_. _Anthia_ is chiefly African, with a few species in India;

_Abacetus_ is wholly African, except a species in Java, and another in

South Europe; and _Hypolithus_ is typically African, but with 7 species in

South America and 1 in Java.

The facts of distribution presented by this important family, looked at

broadly, do not support any other division of the earth into primary

regions than that deduced from a study of the higher animals. The amount of

speciality in each of these regions is so great, that no two of them can be

properly united; and in this respect the Carabidæ accord wonderfully with

the Vertebrates. In the details of distribution there occur many singular

anomalies; but these are not to be wondered at, if we take into

consideration the immense antiquity of Coleopterous insects--which existed

under specialised forms so far back as the Carboniferous epoch,--the ease

with which they may be dispersed as compared with larger animals, and the

facilities afforded by their small size, habits of concealment, and often

nocturnal habits, for adaptation to the most varied conditions, and for

surviving great changes of surface and of the surrounding organic forms.

The wonder rather is, not that there are so many, but so few cases of

exceptional and anomalous distribution; and the fact that these creatures,

so widely different from Vertebrates in organisation and mode of life, are

yet on the whole subject to the same limitations of range as were found to

occur among the higher animals, affords a satisfactory proof that the

principles on which our six primary regions are founded, are sound; and

that they are well adapted to exhibit the most interesting facts of

geographical distribution, among all classes of animals.

Much stress has been laid on the fact of a few species of such typical

European genera as _Carabus_, _Dromius_, and others, being {492}found in

Chili and Temperate South America; and it has been thought, that in a

system of Entomological regions this part of the world must be united to

the Northern Hemisphere. But these writers omit to take into account,

either the large numbers of isolated and peculiar forms characteristic of

South Temperate America, or the indications of affinity with Tropical

America and Australia, both of which are really more important than the

connection with Europe. The three important Chilian genera, _Cascelius_,

_Barypus_, and _Cardiopthalmus_, are closely allied to the Australian

Promecoderus; others, as _Omostenus_ and _Plagiotelium_, are quite

isolated; while _Antarctia_ and _Metius_, according to Lacordaire, form a

distinct division of the family. Chili, too, has many species of

_Pachyteles_, _Coptodera_, and other South American genera; and this

affinity is far stronger in many other families than in the Carabidæ. The

existence of representatives of typical northern forms in Chili, is a fact

of great interest, and may be accounted for in a variety of ways; (see Vol.

II. p. 44) but it is not of such a magnitude as to be of primary importance

in geographical distribution, and it can only be estimated at its fair

value, by taking into account the affinities of all the groups inhabiting

that part of the world.

LUCANIDÆ. (45 Genera, 529 Species.)

Passing over a number of obscure families, we come to the remarkable group

of the Lucanidæ, or Stag-beetles, which, being almost all of large size,

and many of them of the most striking forms, have been very thoroughly

collected and assiduously studied.

The most curious feature of their general distribution, is their scarcity

in Tropical South America, and their complete absence from Tropical North

America and the West Indian Islands, though they appear again in Temperate

North America. In the New World they may, in fact, be looked upon as a

temperate group characteristic of the extra-tropical regions and the

highlands; while in the Old World, where they are far more abundant, they

are distinctly tropical, being especially numerous {493}in the Oriental and

Australian regions. No genus has the range of the whole family, _Dorcus_

and _Lucanus_ being absent from Africa, while _Cladognathus_ is unknown in

the New World and on the continent of Australia. The Oriental region is the

richest in peculiar forms, possessing 16 genera, 7 of which are wholly

confined to it, while 3 others only just range beyond it to North China on

the one side, or to the Austro-Malayan islands on the other. The Australian

region comes next, with 15 genera, of which 7 are wholly peculiar. South

America has 12 genera, 10 of which are peculiar. The Ethiopian region has

10 genera, 7 of which are peculiar, and 2 of these are confined to the

island of Bourbon. The Palæarctic region has 8 genera, and the Nearctic 5;

one genus being peculiar to Europe, and two confined to Europe and North

America. The Ethiopian and Oriental regions have 3 genera in common and

peculiar to them; the Oriental and Australian 3; while the Australian and

Neotropical have 1 in common, to which may be added _Streptocerus_, which

represents in Chili the Australian _Lamprima_.

Among the special features presented by the distribution of the Lucanidæ,

may be mentioned--the remarkable group of genera, _Pholidotus_,

_Chiasognathus_, and _Sphenognathus_, confined to Temperate South America,

the Andes, and mountains of Brazil; _Lucanus_ (19 sp.), almost confined to

the Oriental and Palæarctic regions, three species only inhabiting North

America; _Odontolabris_ (29 sp.), wholly Oriental, with 2 sp. in Celebes;

_Nigidius_ (11 sp.), Ethiopian, but with species in Formosa, the

Philippines, and Malacca; _Syndesus_ (11 sp.), common to Australia, New

Caledonia, and South America; _Figulus_ (20 sp.), divided between Africa

and Madagascar on the one hand, and Australia, with the Malay and Pacific

Islands, on the other.

The facts of distribution here sketched out are in perfect accordance with

those of many groups of Vertebrates. The regions are sharply contrasted by

their peculiar and characteristic genera; the several relations of those

regions are truly indicated; while there is a comparatively small

proportion of cases of anomalous or eccentric distribution.

{494}CETONIIDÆ. (120 Genera, 970 Species.)

As representative of the enormous group of the Lamellicorns, which,

according to continental entomologists, forms a single family numbering

nearly 7,000 species, we take the Cetoniidæ or Rose-Chafers. These comprise

a number of the most brilliant and beautifully-coloured insects, including

the gigantic _Goliathi_, which are among the largest of known beetles. They

have been assiduously collected in every part of the world, and their

classification has been elaborated by many of our most eminent

entomologists.

The Cetoniidæ are especially abundant in tropical and warm countries, yet

far more so in the Old World than in the New; and in the Old World, the

Ethiopian region exhibits a marvellous richness in this family, no less

than 76 genera being found there, while 64, or more than half the total

number, are peculiar to it. Next in richness, though still very far behind,

comes the Oriental region, with 29 genera, 17 of which are peculiar. The

Neotropical has only 14 genera, but all except two are peculiar to it, and

one of these is not found out of the New World. The Australian region has

11 genera, three only being peculiar. The Palæarctic region has 13, with 4

peculiar; the Nearctic 7, with 2 peculiar. The affinities of the regions

for each other, as indicated by the genera confined to two adjacent

regions, are in this family somewhat peculiar. The Ethiopian and Oriental

show the most resemblance, 6 genera being common and peculiar to the two;

the Oriental and the Australian are unusually well contrasted, having only

one genus exclusively in common, while 8 genera are found in the Indo-Malay

Islands which do not cross the boundary to the Austro-Malayan division, and

several others only pass to the nearest adjacent islands; on the other

hand, the only large Australian genus, _Schizorhina_, is found in many

parts of the Moluccas, but not further west. The Australian and Neotropical

regions exhibit no direct affinity, the nearest ally to the South American

Gymnetidæ being _Clinteria_, an African and Asiatic genus; while not a

single genus is common {495}to Australia and South America. The Nearctic

and Palæarctic regions have 3 genera in common, which are found in no other

part of the world.

Among the special features of interest connected with the distribution of

this family, we must first notice the exceptional richness of Madagascar,

which alone possesses 21 peculiar genera. South Africa is also very rich,

having 8 peculiar genera. _Stethodesma_ is very peculiar, being divided

between South America and Mexico on the one hand, and West and South Africa

on the other. _Stalagmosoma_ is a desert genus, ranging from Persia to

Dongola. No genus is cosmopolitan, or even makes any approach to being so,

except _Valgus_, which occurs in all the regions except the Neotropical;

and even the family seems to be not universally distributed, since no

species are recorded either from New Zealand, the Pacific Islands, or the

Antilles.

The facts here brought forward, lead us to the conclusion that the

Cetoniidæ are an Old-World tropical family, which had been well developed

in Africa and Asia before it spread to Australia and America; and that it

is only capable of being freely dispersed in the warmer regions of the

earth. This view will explain the absence of affinity between the

Australian and Neotropical regions, the only closer connection between

which, has almost certainly occurred in the colder portions of the

Temperate zone.

BUPRESTIDÆ. (109 Genera, 2,686 Species.)

The next family suited to our purpose is that of the Buprestidæ, consisting

as it does of many large and some gigantic species, generally adorned with

brilliant metallic colours, and attracting attention in all warm countries.

Although these insects attain their full development of size and beauty

only in the Tropics, they are not much less abundant in the warmer parts of

the Temperate zone. In the Catalogue of the Coleoptera of Europe and the

Mediterranean Basin, by M. de Marseul (1863), we find 317 species of

Buprestidæ enumerated, although {496}the district in question only forms a

part of the Palæarctic region, which would thus seem to possess its full

proportion of the species of this family. Confining ourselves to the

generic forms, we find far less difference than usual between the numbers

possessed by the tropical and the temperate regions; the richest being the

Australian, with 47 genera, 20 of which are peculiar; and the poorest the

Nearctic, with 24 genera, of which 7 are peculiar. The Oriental has 41

genera, 14 of which are peculiar; the Neotropical 39, of which the large

proportion of 18 are peculiar; the Ethiopian 27, of which 6 are peculiar;

and the Palæarctic also 27, but with 9 peculiar.

A most interesting feature in the distribution of this family, is the

strong affinity shown to exist between the Australian and Neotropical

regions, which have 4 genera common to both and found nowhere else; but

besides this, the extensive and highly characteristic Australian genus,

_Stigmodera_, is closely related to a number of peculiar South American

genera, such as _Conognatha_, _Hyperantha_, _Dactylozodes_,--the last

altogether confined to Chili and Temperate South America. Here we have a

striking contrast to the Cetoniidæ, and we can hardly help concluding,

that, as the latter is typically a tropical group, so the present family,

although now so largely tropical, had an early and perhaps original

development in the temperate regions of Australia, spreading thence to

Temperate South America as well as to the tropical regions of Asia and

Africa. The Australian and Oriental regions have 4 genera exclusively in

common, but they also each possess a number of peculiar or characteristic

genera, such as the Indo-Malayan _Catoxantha_ (which has only a single

species in the Moluccas) and nine others of less importance; and the

exclusively Austro-Malayan genus, _Sambus_, with five smaller groups, and

_Cyphogastra_, with only 2 Indo-Malay species. The Oriental and Ethiopian

regions are very distinct, only possessing the single genus, _Sternocera_,

exclusively in common. The Nearctic and Palæarctic are also distinct, only

one genus, _Dicerca_, being confined to America (North and South) and

Europe, a fact which again points to a southern origin for this family, and

its comparatively recent extension into the {497}North Temperate zone. It

must be remembered, however, that in view of the immense geological

antiquity of the existing families of Beetles, dating back certainly to the

Secondary and probably to the Palæozoic epoch, "comparatively recent" may

still be of considerable antiquity.

It is somewhat singular that North and South America have no genera

exclusively in common. The connection between South America and Africa

seems to be shown,--by the genus _Psiloptera_, the mass of the species

being divided between these regions, with a few widely scattered over the

globe; and the American genus _Actenodes_, which has one species in West

Africa. Somewhat allied, is the extensive genus _Polybothris_, strictly

confined to Madagascar. The genus _Agrilus_ is perhaps cosmopolitan,

although no species of the family is recorded from New Zealand. Among the

peculiarities of distribution we may notice,--the genus _Sponsor_, with 8

species in the island of Mauritius, 1 in Celebes, and 1 in New Guinea;

_Ptosima_, scattered between the United States, Mendoza in South Temperate

America, South Europe, the Philippine Islands, and North China;

_Polycesta_, which besides inhabiting South America, North America, and

Europe, has a single species in Madagascar; and _Belionota_, which has 8

species African, 8 Indo-Malayan, 2 Austro-Malayan, and 1 in California. The

extensive genus _Acmæodera_, is most abundant in the warm and dry portions

of the Palæarctic, Ethiopian, and Nearctic regions, with some in the Andes

and South Temperate America, a few in Brazil and the West Indies, and 1

said to be from the Philippines. About one-third of the genera (containing

more than half the species) have a tolerably extensive range, while the

genera confined to single regions contain only about one-fourth of the

total number of species.

It will, I think, be admitted, after a careful study of the preceding

facts, that the regions and sub-regions here adopted, serve to exhibit,

with great clearness, the chief phenomena of distribution presented by this

interesting family.

{498}LONGICORNIA. (1,488 Genera, 7,576 Species).

The elegant and admired group of the Longicorn Beetles, is treated by

continental authors as a single family, consisting of three

sub-divisions--the Prionidæ, Cerambycidæ, and Lamiidæ of English

entomologists. These are so closely related, and are so similar in form,

habits, and general distribution, that it will be best to consider the

whole as one group, noticing whatever peculiarities occur in the separate

divisions. The endless structural differences among these insects, have led

to their being classed in an unusual number of genera, which average little

more than 5 species each; a number far below that in any of the other

families we have been considering, and probably below that which obtains in

any of the more extensive groups of animals or plants. This excessive

subdivision of the genera, a large number of which consist of only one or

two species, renders it difficult to determine with precision the relations

of the several regions, since the affinities of these genera for each other

are in many cases undetermined. A group of such enormous extent as this,

can only be properly understood after years of laborious study; we must

therefore content ourselves with such results as may be obtained from a

general survey of the group, and from a comparison of the range of the

several genera, by means of a careful tabulation of the mass of details

given in the recent Catalogue of Messrs. Gemminger and Harold and the noble

work of Lacordaire.

The proportionate extent of the three families of Longicorns is very

unequal; the Prionidæ comprising about 7 per cent., the Cerambycidæ 44 per

cent., and the Lamiidæ 49 per cent. of the total number of species; and the

genera are nearly in the same proportions, being almost exactly 10, 40, and

50 per cent. of the whole, respectively; or, 135 Prionidæ, 609 Cerambycidæ,

and 746 Lamiidæ. The several regions, however, present marked differences

in their proportions of these families. In the two North Temperate regions,

the Cerambycidæ are considerably more numerous than the Lamiidæ, in the

proportion of about 12 to {499}9; and in this respect the Neotropical

region agrees with them, though the superiority in the proportion of

Cerambycidæ is somewhat less. In the Old World tropical regions, however,

and in Australia, the Lamiidæ greatly preponderate--being nearly double in

the Oriental and Ethiopian regions (or as 11 to 6), while in the Australian

it is as 6 to 5. The Prionidæ show a similar difference, though in a less

degree; being proportionately more numerous in the North Temperate and

Neotropical regions. Now, as regards the North Temperate regions, this

difference can be, to some extent explained, by a difference in the habits

of the insects. The Lamiidæ, which both in the larva and perfect state have

exceedingly powerful jaws, exclusively frequent timber trees, and almost

always such as are dead; while the Cerambycidæ, are generally more delicate

and have weaker mandibles, and many of the species live on shrubs, dead

twigs, foliage, and even on flowers. The immense superiority of the Tropics

in the number and variety of their timber trees, and the extent of their

forests, sufficiently accounts for their superiority to the Temperate

regions in the development of Lamiidæ; but the great excess of Cerambycidæ

in South America as compared with the rest of the Tropics, is not to be so

readily explained.

Bearing in mind the different proportions of the families, as above noted,

we may now consider the distribution of the Longicorns as a whole. In

number of generic forms, the Neotropical region, as in so many other

groups, has a marked superiority. It possesses 516 genera, 489 of which (or

about 19/20 of the whole) are peculiar to it. The Australian and Oriental

regions come next, and are exactly equal, both possessing 360 genera, and

having almost exactly the same proportion (in each case a little less than

¾) peculiar. The Ethiopian region has 262 genera, with about 5/6 peculiar;

the Palæarctic 196, with 51 (rather more than ¼) peculiar; and the Nearctic

111, with 59 (a little more than half) peculiar. The more isolated of the

sub-regions are also well characterised by peculiar genera. Thus, Chili

with Temperate South America possesses 37, a large proportion being

Cerambycidæ; the Malagasi group 26, {500}with a preponderance of Lamiidæ;

and New Zealand 12, of which the Cerambycidæ are only slightly in excess.

The relations between the Longicorn fauna of the several regions, are such

as are in accordance with the dependence of the group on a warm climate and

abundant vegetation; and indicate the efficiency of deserts and oceans as

barriers to their migration. The Neotropical and Australian regions have

only 4 genera in common, but these are sufficient to show, that there must

probably once have been some means of communication between the two

regions, better adapted to these insects than any they now possess. The

Nearctic and Neotropical regions have 5, and the Nearctic and Palæarctic 13

genera in common and peculiar to them, the latter fact being the most

remarkable, because no means of inter-communication now exists, except in

high latitudes where the species of the Longicorns are very few. The

Oriental and Australian regions, on the other hand, are closely connected,

by having no less than 52 genera of Longicorns in common and peculiar to

them. Most of these are specially characteristic of the Malay Archipelago,

often extending over all the islands from Sumatra to New Guinea. This large

number of wide-spread genera of course gives a character of uniformity to

the entire area over which they extend; and, with analogous facts occurring

in other families, has led many entomologists to reject that division of

the Archipelago between the Australian and Oriental regions, which has been

so overwhelmingly demonstrated to be the natural one in the case of the

higher animals. The general considerations already advanced in Chapter II.

enable us, however, to explain such anomalies as this, by the great

facilities that exist for the transfer from island to island of such small

animals, so closely connected with woody vegetation in every stage of their

existence. That this is the true and sufficient explanation, is rendered

clear by certain additional facts, which those who object to the sharp

division of the Indo-Malay and Austro-Malay sub-regions have overlooked.

An analysis of all the Malay Longicorns proves, that besides the 52 genera

characteristic of the Archipelago as a whole, there are 100 genera which

are confined to one or other of its component {501}sub-regions. Many of

these, it is true, consist of single species confined to a single island,

and we will not lay any stress on these; but there are also several

important groups, which extend over the Indo-Malay or the Austro-Malay

islands only, stopping abruptly at the dividing-line between them. For

example, on the Indo-Malay side we have _Euryarthrum_, _Leprodera_,

_Aristobia_, _Coelosterna_, and _Entelopes_, and what is perhaps even more

satisfactory, the large genera _Agelasta_ and _Astathes_, abundant in all

the Indo-Malay islands, but having only one or two species just passing the

boundary into Celebes. On the other side we have _Tethionea_,

_Sphingnotus_, _Arrhenotus_, _Tmesisternus_ (the last three genera

abounding from New Guinea to Celebes, but totally unknown further west),

_Hestima_, _Trigonoptera_, _Amblymora_, _Stesilea_, _Enes_, and the large

genus _Micracantha_, with but a single species beyond the boundary,--30

Austro-Malayan genera in all, each found in more than one island, but none

of them extending west of Celebes. Here we have clear proof that the

boundary line between the two great regions exists for Longicorns, as well

as for all other animals; but in this case an unusually large number have

been able to get across it. This, however, does not abolish the barrier,

but only proves that it is not absolutely effectual in all cases. Those who

maintain that the Malay Archipelago forms a single Coleopterous region,

must disprove or explain the instances of limited range here adduced.

Out of nearly 1500 known genera of these insects, only one genus, _Clytus_,

appears to be cosmopolitan. _Saperda_ and _Callichroma_ are the only others

that perhaps occur in every region; but these are both wanting over wide

tracts of the earth's surface, _Saperda_ being absent from Tropical Africa

and the Malay Archipelago; and _Callichroma_ from the Australian region,

except one species in Polynesia. Many of the genera of Longicorns have a

somewhat wide and scattered distribution, indicative of decadence or great

antiquity. _Mallodon_ and _Parandra_ are mostly South American, but have

species in Australia and Africa; _Oeme_ is found in Brazil and the United

States, with one species in West Africa; _Ceratophorus_ has 2 species in

West Africa and 1 in New Zealand. _Xystrocera_ is mostly African, but has

single species in {502}Borneo, Java, Amboyna and South Australia; _Phyton_

has one species in North America and the other in Ceylon; _Philagetes_ has

2 in South Africa, and 1 in Malacca; _Toxotus_ abounds in North America and

Europe, with one species away in Madagascar. _Leptura_ is also North

Temperate, but has a species at the Cape, one at Singapore and a third in

Celebes. _Necydalis_ has species in North and South America, Europe and

Australia. _Hylotrupes_ has 1 species in North America and Europe, and 1 in

Australia; _Leptocera_ prefers islands, being found only in Ceylon,

Madagascar, Bourbon, Batchian, the New Hebrides, New Caledonia and North

Australia; _Hathliodes_ is Australian, with 1 species in Ceylon;

_Schoenionta_ has 3 Malayan species, and 1 in Natal. Many other cases

equally curious could be quoted, but these are sufficient. They cannot be

held to indicate any close relation between the distant countries in which

species of the same genus are now found, but perhaps serve to remind us

that groups of great antiquity, and probably of great extent, have dwindled

away, leaving a few surviving relics scattered far and wide, the sole

proofs of their former predominance.

_General Observations on the Distribution of Coleoptera._

We have now passed in review six of the most important and best known

groups of the Coleoptera or Beetles, comprising about 2,400 genera, and

more than 21,000 species. Although presenting certain peculiarities and

anomalies, we have found that, on the whole, their distribution is in very

close accordance with that of the higher animals. We have seen reason to

believe that these great and well-marked groups have a high geological

antiquity, and by constantly bearing this fact in mind, we can account for

many of the eccentricities of their distribution. They have probably

survived changes of physical geography which have altogether extinguished

many of the more highly organised animals, and we may perhaps gain some

insight into the bearing of those changes, by considering the cross

relations between the several regions indicated by them. On carefully

tabulating the indications given by each of the groups here discussed, I

arrive at the following approximate result. The {503}best marked affinities

between the regions are those between the Nearctic and Palæarctic,--the

Oriental and Australian,--the Australian and Neotropical,--which appear to

be about equal in each case. Next comes that between the Ethiopian and

Oriental on the one side, and the Ethiopian and Neotropical on the other,

which also appear about equal. Then follows that between the Nearctic and

Neotropical regions; and lastly, and far the least marked, that between the

North Temperate and South Temperate regions. That the relation between the

Ethiopian and Neotropical region should be so comparatively well marked, is

unexpected; but we must consider that in such a comparison as the present,

we probably get the result, not of any recent changes or intermigrations,

but of all the long series of changes and opportunities of migration that

have occurred during many geological epochs,--probably during the whole of

the Tertiary period, perhaps extending far back into the Secondary age.

It appears evident that Insects exhibit in a very marked degree in their

actual distribution, the influence both of very ancient and very modern

conditions of the earth's surface. The effects of the ancient geographical

features of the earth, are to be traced, in the large number of cases of

discontinuous and widely scattered groups which we meet with in almost

every family, and which, to some extent, obscure the broader features of

distribution due to the period during which the barriers which divide the

several primary regions have continued to exist. And this, which we may

consider as the normal distribution, is still further obscured in those

cases where the barriers between existing regions are of such a nature as

to admit of the free passage of insects or their larva in a variety of

ways, and (what is perhaps of more importance) in which the physical

features on both sides of the barrier are so nearly identical, as to admit

of the ready establishment of such immigrants as may occasionally arrive.

These conditions concur, for some families of insects, in the case of the

Oriental and Australian portions of the Malay Archipelago; and it is there

that the normal distribution has been sometimes greatly obscured, but

never, as we have sufficiently shown, by any means obliterated.

{504}CHAPTER XXII.

AN OUTLINE OF THE GEOGRAPHICAL DISTRIBUTION OF MOLLUSCA.

The Mollusca being for the most part marine, it does not enter into the

plan of this work to go into much detail as to their distribution. The

orders and families will, however, be passed briefly in review, and all

terrestrial and fresh-water groups discussed in somewhat more detail; with

the object of showing how far their distribution accords with that of the

higher animals, and to what extent the anomalies they present can be

explained by peculiarities of organisation and habits. If the views

advocated in our fifth chapter are correct, the regions there marked out

must apply to all classes of animals; and it will be the task of the

students of each group, to work out in detail the causes which have led to

any special features of distribution. All I can hope to do here, is to

show, generally and tentatively, that such a mode of treatment is possible;

and that it is not necessary, as it is certainly not convenient or

instructive, to have a distinct set of "Regions" established for each class

or order in the Animal and Vegetable Kingdoms.

For all the Marine groups I have merely summarised the information

contained in Mr. Woodward's _Manual of the Mollusca_, but in the case of

the Land Shells I have consulted the most recent general works, and

endeavoured to give an accurate, though doubtless a very incomplete,

account of the most interesting facts in their distribution. As their

classification is very unsettled, I have followed that of the two latest

great works, by Martens and Pfeiffer.

{505}CLASS.--CEPHALOPODA.

_Order I.--DIBRANCHIATA._

FAMILY 1.--ARGONAUTIDÆ. "Paper Nautilus." (1 Genus, 4 Species).

DISTRIBUTION.--Open seas of all warm regions. Two species fossil in

Tertiary deposits.

FAMILY 2.--OCTOPODIDÆ. "Polypi." (7 Genera, 60 Species).

DISTRIBUTION.--Norway to New Zealand, all tropical and temperate seas and

coasts.

FAMILY 3.--TEUTHIDÆ. "Squids or Sea-pens." (16 Genera, 102 Species.)

DISTRIBUTION.--Universal, to Greenland; 2 other genera are fossil, in the

Lias and Oolite.

FAMILY 4.--SEPIADÆ. "Cuttle Fish." (1 Genus, 30 Species).

DISTRIBUTION.--All seas: 4 other genera are fossil, in Eocene and Miocene

deposits.

FAMILY 5.--SPIRULIDÆ. (1 Genus, 3 Species).

DISTRIBUTION.--All the warmer seas.

{506}FAMILY 6.--BELEMNITIDÆ. Fossil. (6 Genera, 100 Species).

DISTRIBUTION.--Lias to Chalk in Europe, India and North America.

_Order II.--TETRABRANCHIATA._

FAMILY 7.--NAUTILIDÆ. (1 Genus, 3 Species, Living; 4 Genera, 300 Species,

Fossil).

DISTRIBUTION.--Indian and Pacific Oceans; and the fossil species from the

Silurian Period to the Tertiary, in all parts of the world.

FAMILY 8.--ORTHOCERATIDÆ. Fossil. (8 Genera, 400 Species).

DISTRIBUTION.--Lower Silurian to Lias.

FAMILY 9.--AMMONITIDÆ. Fossil. (14 Genera, 1100 Species).

DISTRIBUTION.--Upper Silurian to Chalk. Found at 16,000 feet elevation in

the Himalayas.

{507}Class.--GASTEROPODA.

_Order I.--PROSOBRANCHIATA._

FAMILY 1.--STROMBIDÆ. (4 Genera, 86 Species.)

DISTRIBUTION.--The Strombidæ, or Wing-shells, inhabit tropical and warm

seas from the Mediterranean to New Zealand; most abundant in the Indian and

Pacific Oceans. There are nearly 200 fossil species, from the Lias to

Miocene and recent deposits.

FAMILY 2.--MURICIDÆ. (12 Genera, 1000 Species.)

DISTRIBUTION.--All seas, most abundant in the Tropics. _Trichotropis_ is

confined to Northern seas; _Murex_ and _Fusus_ are cosmopolitan. There are

about 700 fossil species, ranging from the Oolite to the Miocene and recent

formations.

FAMILY 3.--BUCCINIDÆ. (24 Genera, 1100 Species.)

DISTRIBUTION.--The Buccinidæ, or "Whelks," range over the whole world, but

some of the genera are restricted. _Buccinum_ inhabits the north and south

temperate seas; _Monoceros_ the West Coast of America; _Cassidaria_ the

Mediterranean; _Phos_, _Harpa_, _Eburna_, and _Ricinula_, are confined to

the Pacific; _Dolium_ inhabits the Mediterranean as well as the Pacific.

There are about 350 fossil species, mostly from the Eocene and Miocene

beds.

{508}FAMILY 4.--CONIDÆ. (3 Genera, 850 Species.)

DISTRIBUTION.--The Cones are universally distributed, but this applies only

to the genus _Pleurotoma_. _Conus_ is tropical and sub-tropical, and

_Cithara_ is confined to the Philippine Islands. There are about 460 fossil

species, from the Chalk formation to the most recent deposits.

FAMILY 5.--VOLUTIDÆ, (5 Genera, 670 Species.)

DISTRIBUTION.--The Volutes are mostly tropical; but a small species of

_Mitra_ is found at Greenland, and a _Marginella_ in the Mediterranean.

_Cymba_ is confined to the West Coast of Africa and Portugal. _Voluta_

extends south to Cape Horn. There are about 200 fossil species, from the

Chalk and Eocene to recent formations.

FAMILY 6.--CYPRÆIDÆ. (3 Genera, 200 Species.)

DISTRIBUTION.--The well-known Cowries are found all over the world, but

they are much more abundant in warm regions. One small species extends to

Greenland. There are nearly 100 fossil species, from the Chalk to the

Miocene and recent formations.

FAMILY 7.--NATICIDÆ. (5 Genera, 270 species.)

DISTRIBUTION.--The Naticidæ, or Sea-snails, though most abundant in the

Tropics, are found also in temperate seas, and far into the Arctic regions.

Two other genera are fossil; and there are about 300 extinct species,

ranging from the Devonian to the Pliocene formations.

{509}FAMILY 8.--PYRAMIDELLIDÆ. (10 Genera, 220 Species.)

DISTRIBUTION.--These turreted shells are very widely distributed both in

temperate and tropical seas; and most of the genera have also a wide range.

There are about 400 extinct species, from so far back as the Lower Silurian

to the Pliocene formations.

FAMILY 9.--CERITHIADÆ. (5 Genera, 190 Species.)

DISTRIBUTION.--These are marine, estuary, or fresh-water shells, of an

elongated spiral form; they have a world-wide distribution, but are most

abundant in the Tropics. _Potamides_ (41 sp.), is the only fresh-water

genus, and is found in the rivers of Africa, India and China, to North

Australia and California. Another genus is exclusively fossil, and there

are about 800 extinct species, ranging from the Trias to the Eocene and

recent formations.

FAMILY 10.--MELANIADÆ. (3 Genera, 410 Species.)

DISTRIBUTION.--Fresh-water only: lakes and rivers in warm countries, widely

scattered. South Palæarctic and Australian regions, from Spain to New

Zealand; South Africa, West Africa, and Madagascar; United States. There

are about 50 fossil species, from the Wealden and Eocene to recent

formations.

FAMILY 11.--TURRITELLIDÆ. (5 Genera, 230 Species.)

DISTRIBUTION.--Universal. _Cæcum_ is found in north temperate seas only.

The other genera are mostly tropical, but some species reach Iceland and

Greenland. There are near 300 species fossil, ranging from the Neocomian to

the Pliocene formations.

{510}FAMILY 12.--LITTORINIDÆ. (9 Genera, 310 Species.)

DISTRIBUTION.--The Littorinidæ are mostly found on the coasts in shallow

water; as the common Periwinkle (_Littorina littorea_). They are of

world-wide distribution; but _Solarium_ and _Phorus_ are tropical; while

_Lacuna_, _Skenea_, and most species of _Rissoa_ are Northern. About 180

species are fossil, ranging from the Permian to the Pliocene formations.

FAMILY 13.--PALUDINIDÆ. (4 Genera, 217 Species.)

DISTRIBUTION.--The Paludinidæ, or River-snails, are all fresh-water, and

range over the whole world. _Paludina_ (60 sp.), is confined to the

Northern Hemisphere; _Ampullaria_ (136 sp.), is tropical; _Amphibola_ (3

sp.), inhabits New Zealand and the Pacific Islands; _Valvata_ (18 sp.),

North America and Britain. There are 72 fossil species of _Paludina_ and

_Valvata_, in the Wealden formation and more recent fresh-water deposits.

FAMILY 14.--NERITIDÆ. (10 Genera, 320 Species.)

DISTRIBUTION.--All warm seas, ranging north to Norway and the Caspian Sea.

_Neritina_ and _Navicella_ inhabit fresh or brackish waters, the latter

confined to the countries bordering the Indian Ocean and the islands of the

Pacific. There are 80 fossil species, from the Trias, Lias, and Eocene

formations down to recent deposits.

FAMILY 15.--TURBINIDÆ. (10 Genera, 425 Species).

DISTRIBUTION.--The genus TROCHUS (200 sp.) has a world-wide range, but the

other genera are mostly tropical, and are most abundant in the Indian and

Pacific Oceans. There are more than 900 fossil species, found in all parts

of the world, from the Lower Silurian to the Tertiary formations.

{511}FAMILY 16.--HALIOTIDÆ. (6 Genera, 106 Species).

DISTRIBUTION.--The Ear-shells are most abundant in the Indian and Pacific

Oceans; some are found on the east coasts of the Atlantic, but there are

very few in the West Indies. _Ianthina_ (10 sp.) consists of floating

oceanic snails found in the warm parts of the Atlantic. Three other genera

are fossil, and there are near 500 fossil species of this family ranging

from the Lower Silurian to the Pliocene formations.

FAMILY 17.--FISSURELLIDÆ. (5 Genera, 200 Species).

DISTRIBUTION.--All seas. _Puncturella_ (6 sp.) is confined to Northern and

Antarctic seas; _Rimula_ to the Philippines; and _Parmophorus_ (15 sp.)

from the Cape of Good Hope to the Philippines and New Zealand. There are

about 80 fossil species, ranging from the Carboniferous formation to the

deposits of the Glacial epoch.

FAMILY 18.--CALYPTRÆIDÆ. (4 Genera, 125 Species).

DISTRIBUTION.--The Calptræidæ, or Bonnet-Limpets, are found on the coasts

of all seas from Norway to Chili and Australia; but are most abundant

within the Tropics. The genera are all widely scattered. There are 75

fossil species, ranging from the Devonian to recent formations.

FAMILY 19.--PATELLIDÆ. (4 Genera, 254 Species).

DISTRIBUTION.--The Patellidæ, or Limpets, are universally distributed, and

are as abundant in the temperate as in tropical seas. There are about 100

fossil species, ranging from the Silurian to the Tertiary formations.

{512}FAMILY 20.--DENTALIADÆ. (1 Genus, 50 Species).

DISTRIBUTION.--The genus _Dentalium_ is found in the North Atlantic,

Mediterranean, West Indies and India. There are 125 fossil species, found

in various formations as far back as the Devonian in Europe and in Chili.

FAMILY 21.--CHITONIDÆ. (1 Genus, 250 Species).

DISTRIBUTION.--On rocky shores in all parts of the world. There are 37

fossil species ranging back to the Silurian period.

_Order II.--PULMONIFERA. ("Terrestrial Molluscs.")_

The Land and Fresh-water snails are so important and extensive a group, and

their classification has been so carefully studied, that their geographical

distribution is a subject of much interest. The range of the genera will

therefore be given in some detail. For the Helicidæ I follow the classical

work of Albers--_Die Helicien_, Von Martens' Edition (1860); and for the

Operculate families, Pfeiffer's _Monographia Pneumonopomorum Viventium_,

2nd Supplement, 1865. The number of species is, of course, very

considerably increased since these works were published (and the probable

amount of the increase I have in most cases indicated), but this does not

materially affect the great features of their geographical distribution.

FAMILY 22.--HELICIDÆ. (33 Genera, 3,332 Species) (1860).

GENERAL DISTRIBUTION.--Universal.

The Helicidæ, or Snails, are a group of immense extent and absolutely

cosmopolitan in their range, being found in the most barren deserts and on

the smallest islands, all over the globe. They reach to near the line of

perpetual snow on mountains, and {513}to the limit of trees or even

considerably beyond it, in the Arctic regions; but they are comparatively

very scarce in all cold countries. The Antilles, the Philippine Islands,

Equatorial America, and the Mediterranean sub-region are especially rich in

this family. Comparatively few of the genera, and those generally small

ones, are restricted to single regions; but on the other hand very few are

generally distributed, only two--_Helix_ and _Pupa_--occurring in all the

six regions, while _Helix_ alone is truly cosmopolitan, occurring in every

sub-region, in every country, and perhaps in every island on the globe.

The Neotropical region is, on the whole, the richest in this family, the

continental Equatorial districts producing an abundance of large and

handsome species, while the Antilles are pre-eminent for the number of

their peculiar forms. This region possesses 22 of the genera, and 6 of them

are peculiar.

The Palæarctic region seems to come next in productiveness, but this may be

partly owing to its having been so thoroughly explored. It possesses 16 of

the genera, and 3 of them are confined to it. The great mass of the species

are found in the warm and fertile countries surrounding the Mediterranean

Sea.

The Ethiopian region has 13 genera, only one of which is peculiar.

The Australian region has 14 genera, 2 of which are confined to the Pacific

Islands.

The Oriental has 15 genera and the Nearctic 12, but in neither case are

there any peculiar generic types.

The following is the distribution of the several genera taken in the order

of their magnitude:--

_Helix_ (1,115 sp.), cosmopolitan. This genus is divided into 88

sub-genera, a number of which have a limited distribution. An immense

quantity of species have been recently described, so that the number now

exceeds 2,000.

_Nanina_ (290 sp.) is characteristic of the Oriental and Australian

regions, over the whole of which it extends, just entering the Palæarctic

region as far as North China and Japan. Isolated from this area is a small

group of 4 species occurring {514}in West Africa. The number of species in

this genus have now been increased to about 400.

_Clausilia_ (272 sp.) is most abundant in Europe, with a few species widely

scattered in India, Malaya, China, Japan, Equatorial America, and one in

Porto Rico. The described species have been increased to nearly 500.

_Bulimulus_ (210 sp.) is American, and almost exclusively Neotropical,

ranging from Montevideo and Chili, to the West Indian Islands, California

and Texas; with two sub-genera confined to the Galapagos Islands. About 100

new species have been described since the issue of the second edition of

Dr. Woodward's Manual.

_Pupa_ (210 sp.) abounds most in Europe and the Arctic regions, but has a

very wide range, being scattered throughout Africa, continental India,

Australia, the Pacific Islands, North America to Greenland, and the

Antilles; but it is absent from South America, the Himalayan and Malayan

sub-regions, China and Japan. An extinct species has occurred abundantly in

the carboniferous strata of North America. About 160 additional species

have been described.

_Bulimus_ (172 sp.) abounds most in Tropical South America; it is also

found from Burmah eastward through Malaya to the Solomon and Fiji Islands;

there are also scattered species in Patagonia, St. Vincents, Texas, St.

Helena, and New Zealand. More than 100 additional species have been

described.

_Buliminus_ (132 sp.) ranges from Central and South Europe over the whole

Ethiopian and Oriental regions to North China, and through the Australian

to New Zealand; there is also a single outlying species in the Galapagos

Islands. About 50 more species have been described.

_Cochlostyla_ (127 sp.) is almost peculiar to the Philippine Islands,

beyond which, are a species in Borneo, one in Java, and two in Australia.

Very few new species have been added to this genus.

_Achatinella_ (95 sp.) is absolutely confined to the Sandwich Island group.

Recent researches have more than tripled the number of described species.

{515}_Achatina_ (87 sp.) is most abundant and finest in the Ethiopian

region, over the whole of which it ranges; but there are also species in

Florida, the Antilles, the Sandwich Islands, Ceylon and India. The

described species are now more than doubled.

_Hyalina_ (84 sp.) inhabits all Tropical America and the Antilles, North

America to Greenland, and Europe to the Arctic regions. Comparatively few

new species have been described.

_Cylindrella_ (83 sp.) inhabits the West Indian islands and Guatemala to

Texas, with a sub-genus in the Philippine Islands. Species since described

have more than trebled the number in this genus.

_Cionella_ (67 sp.) is widely scattered; in India from Ceylon to the Khasia

Mountains, Brazil, New Granada, the West Indian islands, Palæarctic, and

northern part of Nearctic regions, Pacific Islands, New Zealand, and Juan

Fernandez. About 20 new species have since been described.

_Glandina_ (66 sp.), Peru to South Carolina and the Antilles, with three

species in Central Africa and one in South Europe. About 40 species have

been added to this genus.

_Stenogyra_ (49 sp.), widely distributed: Tropical America and West Indies

to Florida, South and West Africa, the Mediterranean region, India and the

Philippines. About a dozen new species have been described.

_Succinea_ (41 sp.), widely scattered in all the regions, and in St.

Helena, Juan Fernandez, Tahiti, Chiloe, Greenland, West Africa, Himalayas

and Australia. The described species are now more than 100.

_Partula_ (39 sp.), Solomon Islands to Tahiti and Sandwich Islands. This

genus has also been increased to near 100 species.

_Streptaxis_ (34 sp.), most abundant in Tropical South America, but occurs

in West Africa, the Seychelles and Rodriguez Islands, Ceylon and Burmah. It

now contains over 100 described species.

_Spiraxis_ (33 sp.), Yucatan to Mexico, and less abundant in the West

Indian Islands. About 20 species have been added.

{516}_Macroceramus_ (27 sp.), Antilles, Florida, and Peru. The species have

been more than doubled.

_Vitrina_ (26 sp.), widely scattered through North and Central Europe,

North-west America and Greenland, Abyssinia, Madagascar and South Africa,

Himalayas to Burmah and Australia. Species since described have more than

doubled the number in this genus.

_Orthalicus_ (23 sp.), Bolivia to Mexico and Antilles. This genus has been

increased to about 40 species.

_Sagda_ (19 sp.), Antilles only. Very few new species, if any, have been

described.

_Zonites_ (12 sp.), South Europe, with one species of a distinct type in

Guatemala. The number of species in this genus has been since about

tripled.

_Leucochroa_ (11 sp.), Mediterranean region to Syria and Arabia Petrea.

_Simpulopsis_ (7 sp.), Bahia, Antilles, and far away in the Solomon

Islands. Two or three have been added.

_Balea_ (6 sp.), Middle and North Europe, Brazil, and the Island of Tristan

d'Acunha.

_Daudebardia_ (6 sp.), Central and South Europe; and a species has since

been discovered in New Zealand.

_Macrocycles_ (4 sp.), Chili, California, Oregon and Central North America.

_Columna_ (3 sp.), West Africa, Princes Islands and Madagascar.

_Stenopus_ (2 sp.), Island of St. Vincent (West Indies.)

_Pfeifferia_ (2 sp.), Philippines and Moluccas.

_Testacella_ (2 sp.), West Europe and Teneriffe. About 8 species have been

since described, including one from New Zealand.

Fossil species of _Helix_, _Bulimus_, _Achatina_, _Balea_, and _Clausilia_,

are found in all the Tertiary formations; while a species of _Pupa_ (as

already stated) occurs in the carboniferous formation. For interesting

details of the distribution of the sub-genera and species of _Achatinella_

in the Sandwich Islands, see a paper by Rev. J. T. Gulick in the _Journal

of the Linnean Society_. (Zoology, vol. xi. p. 496.)

{517}FAMILY 23.--LIMACIDÆ.--(12 Genera, 116 Species.)

GENERAL DISTRIBUTION.

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The Limacidæ, or Slugs, are widely distributed, but they are absent from

South America, where they are represented by the next family. They also

seem to be absent from the greater part of Africa. The genera are

distributed as follows:--

_Limax_ (51 sp.), Palæarctic region, Australia and the Sandwich Islands;

_Anadenus_ (2 sp.), Himalayas; _Philomychus_ (9 sp.), North America, China

and Java; _Arion_ (25 sp.), Norway to Spain and South Africa; _Parmacella_

(7 sp.), South Europe, Canary Islands and North India; _Janella_ (1 sp.),

New Zealand; _Aneitea_ (1 sp.), New Hebrides and New Caledonia; _Parmarion_

(4 sp.), India; _Triboniophorus_ (3 sp.), Australia; _Testacella_ (3 sp.),

South Europe, Canary Islands, and New Zealand; _Hyalimax_ (2 sp.), Bourbon

and Mauritius; _Krynickia_ (8 sp.), Eastern Europe and North America. A few

species of _Limax_, _Arion_, and _Testacella_ have been found fossil in

Tertiary deposits.

FAMILY 24.--ONCIDIADÆ. (2 Genera, 36 Species.)

GENERAL DISTRIBUTION.

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The Oncidiadæ, or Slugs with a coriaceous mantle, inhabit the Oriental

region, Mauritius, Australia, the Pacific Islands, South America and South

Europe. The genera are:--

{518}_Oncidium_ (16 sp.), South Europe (1 sp. British), Mauritius,

Australia and Pacific Islands; Vaginulus (20 sp.), Neotropical and Oriental

regions.

FAMILY 25.--LIMNÆIDÆ. (7 Genera, 332 Species.)

GENERAL DISTRIBUTION.

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1. 2. 3. 4 |1. 2. 3. 4 |1. 2. 3. 4 |-- -- 3 -- |1. 2. 3. 4 |-- -- -- --

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The Limnæidæ, or Fresh-water Snails, inhabit ponds and rivers in most parts

of the world, but appear to be absent from the Australian region. The

genera are distributed as follows:--

_Limnæa_ (95 sp.), Nearctic, Palæarctic, and Oriental regions;

_Choanomphalos_ (2 sp.), Lake Baikal; _Pompholyx_ (2 sp.), Western America;

_Chilinia_ (18 sp.), South America; _Physa_ (20 sp.), Nearctic, Palæarctic,

Ethiopian and Oriental regions, and extends to above 73° North Latitude in

Siberia, being the most Arctic of land or fresh-water shells; _Ancylus_ (49

sp.), Nearctic and Neotropical regions, Europe and New Zealand; _Planorbis_

(145 sp.), Nearctic, Palæarctic and Oriental regions. Several genera are

found fossil, chiefly in the Wealden, Eocene, and Miocene formations.

FAMILY 26.--AURICULIDÆ. (3 Genera, 210 Species.)

GENERAL DISTRIBUTION.

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The Auriculidæ are chiefly found near the sea in hot countries, and are

most abundant in the Eastern tropics. They are absent {519}from the East

coast of South America. The genera have a somewhat restricted distribution

as follows:--

_Auricula_ (128 sp.), India, Pacific Islands, Peru and West Indies;

_Melampus_ (56 sp.), West Indies and Europe; _Carychium_ (9 sp.), Europe

and North America; _Plectrotrema_ (14 sp.), Australia, Malay Islands,

China, Cuba; _Blauneria_ (2 sp.), West Indian and Sandwich Islands. There

are many fossil species ranging back to the Eocene formation.

FAMILY 27.--ACICULIDÆ. (4 Genera, 65 Species.) (1865.)

GENERAL DISTRIBUTION.

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The Aciculidæ are small cylindrical shells chiefly found in the West Indian

Islands, but with representatives widely scattered over the globe.

_Acicula_ (5 sp.) is European only; _Geomelania_ (21 sp.), and _Chittya_ (1

sp.), are confined to the Island of Jamaica; _Truncatella_ (38 sp.), is

most abundant in the Antilles, but is also found in some part of each of

the six regions, as indicated by the diagram of the family. But few new

species have been added to this group.

FAMILY 28.--DIPLOMMATINIDÆ. (3 Genera, 23 Species.) (1865.)

GENERAL DISTRIBUTION.

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The Diplommatinidæ are minute shells of the Oriental and Australian

regions.

{520}_Diplommatina_ (18 sp.) inhabits India to Burmah, and the greater part

of the Australian region; the number of species has now been doubled, and

one has been discovered in the island of Trinidad; _Clostophis_ (1 sp.),

Moulmein; _Paxillus_ (3 sp.), Borneo, Hong Kong, and Loo Choo Islands.

FAMILY 29.--CYCLOSTOMIDÆ. (41 Genera, 1009 Species.) (1865.)

GENERAL DISTRIBUTION.

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This extensive group, comprising the largest of the operculated

land-shells, is especially characteristic of the Oriental region, which

possesses 25 genera, no less than 12 of them being wholly confined to it.

The Neotropical region comes next, with 15 genera, 9 of which are peculiar;

but a large number of these are confined to the West Indian Islands, South

America itself being very poor in this group. The Palæarctic region has 3

peculiar genera; the Ethiopian and Australian 1 each. The Nearctic region

has but a single West Indian species in Florida. The distribution of the

genera is as follows:--

Peculiar to or characteristic of the Oriental region are, _Opisthoporus_

(11 sp.), _Rhiostoma_ (6 sp.), _Alycaeus_ (39 sp.), _Opisthostoma_ (1 sp.),

_Hybocistis_ (3 sp.), _Pterocyclos_ (19 sp.), extending to the Moluccas;

_Aulopoma_ (4 sp.), _Dermatocera_ (4 sp.), _Leptopoma_ (54 sp.), extending

west to the Seychelles and east to the Moluccas and New Guinea;

_Cyclophorus_ (163 sp.), most abundant in the Oriental region, but ranges

to Japan, to Chili, and all Tropical America, over the whole Australian

region, and to Natal and Madagascar; _Cataulus_ (15 sp.), confined to

Ceylon, the Neilgherries and Nicobar Islands; _Rhaphaulus_ (4 sp.), Penang

to Ceram; _Streptaulus_ (1 sp.), _Arinia_ (3 sp.), _Pupinella_ (2 sp.),

_Pupina_ (24 sp.), half in North India to Philippines and {521}Japan, the

other half in Moluccas, New Guinea and Australia; _Cyclotopsis_ (2 sp.),

India and Malaya; _Registoma_ (9 sp.), Philippines and Moluccas, New

Caledonia and Pacific.

Characteristic of the Neotropical region are:--_Cyclotus_ (111 sp.), half

in the Antilles and Tropical America, the rest in the Moluccas, China,

Malaya, India, Natal, and the Seychelle Islands; _Megalomastoma_ (27 sp.),

abundant in Cuba, West Indies and South America, others in India, Malaya,

and Mauritius; _Jamaicia_ (2 sp.), Jamaica; _Licina_ (5 sp.), Antilles;

_Choanopoma_ (49 sp.), Antilles; _Ctenopoma_ (25 sp.), Antilles;

_Diplopoma_ (1 sp.), Cuba; _Adamsiella_ (15 sp.), Jamaica, Cuba, Guatemala;

_Cyclostomus_ (113 sp.), abundant in Antilles, also occurs in Madagascar,

Arabia, Syria, Hungary and New Zealand; _Tudora_ (34 sp.), Antilles, and

one species in Algeria; _Cistula_ (40 sp.), _Chondropoma_ (94 sp.),

_Bourcieria_ (2 sp.), Tropical America.

Peculiar to or characteristic of the Palæarctic region are:--_Craspedopoma_

(5 sp.), confined to Madeira, the Azores and Canaries; _Leonia_ (1 sp.),

Spain and Algeria; _Pomatias_ (22 sp.), Europe and Canaries with a species

in the Himalayas; _Cecina_ (1 sp.), Manchuria.

The Ethiopian region has the peculiar genus _Lithodion_ (5 sp.),

Madagascar, Socotra and Arabia; and _Otopoma_ (19 sp.), Mascarene Islands

and Socotra, with a species in Western India and another in New Ireland.

The Australian region is characterised by _Callia_ (3 sp.), in Ceram,

Australia, and the Philippines respectively; _Realia_ (7 sp.), New Zealand

and the Marquesas Islands; _Omphalotropis_ (38 sp.), the Australian region,

with some species in India, Malaya, and the Mauritius.

The remaining genus, _Hydrocena_ (27 sp.), has a very widely scattered

distribution, being found in South Europe, Japan, the Cape, China, Malaya,

New Zealand, the Pacific Islands and Chili. From 10 to 20 per cent. of new

species have been since described in most of the genera of this family.

{522}FAMILY 30.--HELICINIDÆ. (7 Genera, 433 Species.) (1868.)

GENERAL DISTRIBUTION.

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The Helicinidæ are very characteristic of the Antilles, comparatively few

being found in any other part of the world except the Islands of the

Pacific. The genera are:--

_Trochatella_ (33 sp.), Antilles with a species in Venezuela, and another

in Cambodja; _Lucidella_ (5 sp.), Antilles; _Helicina_ (274 sp.), Antilles,

Pacific Islands, Tropical America, Southern United States, Moluccas,

Australia, Philippines, Java, Andaman Islands and North China;

_Schasicheila_ (5 sp.), Mexico, Guatemala and Bahamas; _Alcadia_ (28 sp.),

Antilles; _Georissa_ (5 sp.) Moulmein to Burmah. About 10 per cent. of new

species appear to have been since described in the larger genera of this

family.

_General Observations on the Distribution of the Land Mollusca._

A consideration of the distribution of the families and genera of

land-shells shows us, that although they possess some special features, yet

they agree in many respects with the higher animals in their limitation by

great natural barriers, such as oceans, deserts, mountain ranges, and

climatal zones. A remarkable point in the distribution of these animals, is

the number of genera which have a very limited range, and also the

prevalence of genera having species scattered, as it were at random, all

over the earth. No less than 14 genera (or about one-sixth of the whole

number) are confined to the Antilles, while the greater part of the

sub-genera of modern authors are restricted to limited areas.

If we first compare the New World with the Old, we find the difference as

regards genera quite as great as in most of the {523}vertebrates. In the

Helicidæ, 10 genera are confined to the New, and 7 to the Old World, 16

being common to both. In the Operculata the number of genera of restricted

range is greater,--the New World having 15, the Old World 32 genera, only 8

being common to both. Of the New World genera 12 out of the 15 do not occur

at all in South America; and of those of the Old World, 22 out of the 32

occur in a single region only. If we take the northern and southern

division proposed by Professor Huxley (the latter comprising the Australian

and Neotropical regions), we find a much less well-marked diversity. Among

the Helicidæ only 4 are exclusively northern, 8 southern; while among the

Operculata 22 are northern, 16 southern. The best way to compare these two

kinds of primary division will be to leave out all those genera confined to

a single region each, and to take account only of those characteristic of

two or more of the combined regions; which will evidently show which

division is the most natural one for this group. The result is as

follows:--

GENERA COMMON TO TWO OR MORE REGIONS IN, AND CONFINED TO, EACH PRIMARY

DIVISION OF THE EARTH.

Helicidæ Operculata. Totals.

{ Northern 0 0 0 }

{ Southern 0 0 0 }

{ Old World 1 12 13 }

{ New World 4 0 4 }

We find then that the northern and southern division of the globe is not at

all supported by the distribution of the terrestrial molluscs. It is indeed

very remarkable, that the connection so apparent in many groups between

Australia and South America is so scantily indicated here. The only facts

supporting it seem to be, the occurrence of _Geotrochus_ (a sub-genus of

Helix) in Brazil, as well as in the Austro-Malayan and West Pacific Islands

and North Australia; and of _Bulimus_ in the same two parts of the globe,

but peculiar sub-genera in each. But in neither case is there any affinity

shown between the temperate portions of the two regions, so that we must

probably trace this resemblance to some more ancient diffusion of types

than that which led to the similarity of plants and insects. Still more

curious is the entire {524}absence of genera confined to, and

characteristic of Africa and India. One small sub-genus of _Helix_,

(_Rachis_), and one of _Achatina_, (_Homorus_), appear to have this

distribution,--a fact of but little significance when we find another

sub-genus of _Helix_, (_Hapalus_), common and confined to Guinea and the

Philippine Islands; and when we consider the many other cases of scattered

distribution which cannot be held to indicate any real connection between

the countries implicated. No genus is confined to the Palæarctic and

Nearctic regions as a whole. A large number of sub-genera, many of them of

considerable extent, are peculiar to one or other of these regions, but

only 3 sub-genera of _Helix_ and 2 of _Pupa_ are common and peculiar to the

two combined, and these are always such as have an Arctic range and whose

distribution therefore offers no difficulty.

We find, then, that each of our six regions and almost all of our

sub-regions are distinctly confirmed by the distribution of the terrestrial

mollusca; while the different combinations of them which have at various

times been suggested, receive little or no support whatever. Even those

remarkably isolated sub-regions, New Zealand and Madagascar, have no

strictly peculiar genera of land-shells, although they both possess several

peculiar sub-genera; being thus inferior in isolation to some single West

Indian Islands, to the Sandwich Islands, and even to the North Atlantic

Islands (Canaries, Madeira, and Azores), each of which have peculiar

genera. This of course, only indicates that the means by which land

mollusca have been dispersed are somewhat special and peculiar. To

determine in what this speciality consists we must consider some of the

features of the specific distribution of this group.

The range of genera, and even of sub-genera is, as we have seen, often wide

and erratic, but as a general rule the species have a very restricted area.

Hardly a small island on the globe but has some land-shells peculiar to it.

Juan Fernandez has 20 species, all peculiar. Madeira and Porto Santo have

109 peculiar species out of a total of 134. Every little valley, plain, or

hill-top, in the Sandwich Islands, though only a few square miles in

extent, has its {525}peculiar species of _Achatinella_. Another striking

feature of the distribution of land molluscs, is the richness of islands as

compared with continents. The Philippines contain more species than all

India; and those of the Antilles according to Mr. Bland almost exactly

equal the numbers found in the entire American continent from Greenland to

Patagonia. Taking the whole world, it appears that many more species of

land-shells are found in the islands than on the continents of the globe, a

peculiarity that obtains in no other extensive group of animals.

Looking at these facts it seems probable, that the air-breathing molluscs

have been chiefly distributed by air- or water-carriage, rather than by

voluntary dispersal on the land. Even seas and oceans have not formed

impassable barriers to their diffusion; whereas they only spread on dry

land with excessive slowness and difficulty. The exact mode in which their

diffusion is effected is not known, and it may depend on rare and

exceptional circumstances; but it seems likely to occur in two ways. Snails

frequently conceal themselves in crevices of trees or under bark, or attach

themselves to stems or foliage, and either by their operculum or mucous

diaphragm, are able to protect themselves from the injurious effects of

salt water for long periods. They might therefore, under favourable

conditions, be drifted across arms of the sea or from island to island;

while wherever there are large rivers and occasional floods, they would by

similar means be widely scattered over land areas. Another possible mode of

distribution is by means of storms and hurricanes, which would carry the

smaller species for long distances, and might occasionally transport the

eggs of the larger forms. Aquatic birds might occasionally get both shells

and eggs attached to their feet or their plumage, and convey them across a

wide extent of sea. But whether these, or some other unknown agency has

acted, the facts of distribution clearly imply that some means of transport

over water is, and has been, the chief agent in the distribution of these

animals; but that its action is very rare or intermittent, so that its

effects are hardly perceptible in the distribution of single species.

Another important factor in enabling us to account for the

{526}distribution of these animals is the geological antiquity of the

group, and the amount of change exhibited in time, by species and genera.

Now we find that most of the genera of land-shells range back to the Eocene

period, while those inhabiting fresh water are found almost unchanged in

the Wealden. In North America a species of _Pupa_ and one of _Zonites_,

have been discovered in the coal measures, along with Labyrinthodonts; and

this fact seems to imply, that many more terrestrial molluscs would be

discovered, if fresh-water deposits, made under favourable conditions, were

more frequently met with in the older rocks. If then the existing groups of

land-molluscs are of such vast antiquity, and possess some means, however

rarely occurring, of crossing seas and oceans, we need not wonder at the

wide and erratic distribution now presented by so many of the groups; and

we must not expect them to conform very closely to those regions which

limit the range of animals of higher organization and less antiquity.

The total number of species of pulmoniferous mollusca is about 7,000,

according to the estimate of Mr. Woodward, brought down to 1868 by Mr.

Tate. But this number would be largely increased if the estimates of

specialists were taken. Mr. Woodward for example, gives 760 as the number

of species in the West Indian Islands; whereas Mr. Thomas Bland, who has

made the shells of these islands a special study, considers that there were

1,340 species in 1866. So, the land-shells of the Sandwich Islands are

given at 267; but Mr. Gulick has added 120 species of Achatinellidæ,

bringing the numbers up to nearly 400,--but no doubt several of these are

so closely related that many conchologists would class them as varieties.

The land-shell fauna of the Antilles is undoubtedly the most remarkable in

the world, and it has been made the subject of much interesting discussion

by Mr. Bland and others. This fauna differs from that of all other parts of

the globe in the proportions of the operculate to the inoperculate shells.

The Operculata of the globe are about one-seventh, the Inoperculata about

six-sevenths of the whole; and some general approximation to this

proportion (or a much smaller one) exists in almost all the continents,

islands, and {527}archipelagoes. In the Philippines, for example, the

proportion of the Operculata is a little more than one-seventh; in the

Mauritius, between one-third and one-fourth; in Madeira, one-fourteenth; in

the whole American continent about one-eighth; but when we come to the

Antilles we find them to amount to nearly five-sixths, about half the

Operculata of the globe being found there!

Mr. Bland endeavours to ascertain the source of some of the chief genera

found in the West Indian Islands, on the principle that "each genus has had

its origin where the greatest number of species is found;" and then

proceeds to determine that some have had an African, some an Asiatic, and

some an American origin, while others are truly indigenous. But we fear

there is no such simple way of arriving at so important a result; and in

the case of groups of extreme antiquity like the genera of mollusca, it

would seem quite as possible that the origin of a genus is generally _not_

where the greatest number of species are now found. For during the repeated

changes of physical conditions that have everywhere occurred since the

Eocene period (to go no further back) every genus must have made extensive

migrations, and have often become largely developed in some other district

than that in which it first appeared. As a proof of this, we not

unfrequently find fossil shells where the species and even the genus now no

longer exists; as _Auricula_, found fossil in Europe, but only living in

the Malay and Pacific Islands; _Anastoma_ and _Megaspira_, now peculiar to

Brazil, but fossil in the Eocene of France; and _Proserpina_ of the West

Indies, found in the Eocene formation of the Isle of Wight. The only means

by which the origin of a genus can satisfactorily be arrived at, is by

tracing back its fossil remains step by step to an earlier form; and this

we have at present no means of doing in the case of the land-shells. Taking

existing species as our guide we should certainly have imagined that the

genus _Equus_ originated in Africa or Central Asia; but recent discoveries

of numerous extinct species and of less specialized forms of the same type,

seem to indicate that it originated in North America, and that the whole

tribe of "horses" may be, for anything we yet know {528}to the contrary,

recent immigrants into the Old World! This example alone must convince us,

that it is impossible to form any conclusion as to the origin of a genus,

from the distribution of existing species only.

The general conclusion we arrive at, therefore, is, that the causes that

have led to the existing distribution of the genera and higher groups of

the terrestrial mollusca are so complex, and have acted through such long

periods, that most of the barriers which limit the range of other

terrestrial animals do not apply to them, although the species are, in most

cases, strictly limited by them. Some means of diffusion--which, though

probably acting very slowly and at long intervals, and more powerfully on

continents than between islands, is yet highly efficient when we consider

the long duration of genera--has, to a considerable extent, dispersed them

across continents, seas, and oceans. On the other hand, those mountain

barriers which separate many groups of the higher vertebrates, are

generally less ancient than the genera of land-shells, which are thus often

distributed independently of them. In order to compare the distribution of

the terrestrial mollusca on equal terms with those of land animals

generally, we must take genera of the former as equivalent to family groups

of the latter; and we shall, I believe, then find that the distribution of

the sub-genera and smaller groups of species do accord mainly with those

divisions of the earth into regions and sub-regions which we have here

indicated. Mr. Harper Pease, in a communication on Polynesian Land Shells

in the _Proceedings of the Zoological Society_ for 1871 (p. 449), marks out

the limits of the Polynesian sub-region, so as exactly to agree with that

arrived at here from a consideration of the distribution of vertebrata; and

he says that this sub-region, (or region, as he terms it) is distinctly

characterised by its land-shells from all the surrounding regions. The

genera (or sub-genera) _Partula_, _Pitys_, _Achatinella_, _Palaina_,

_Omphalotropis_, and many others, are either wholly confined to this

sub-region or highly characteristic of it. Mr. Binney, in his _Catalogue of

the Air-breathing Molluscs of North America_, marks out our Nearctic region

(with almost identical limits) as most clearly {529}characterised. He also

arrives at a series of sub-divisions, which generally (though not exactly)

agree with the sub-regions which I have here adopted. The Palæarctic, the

Ethiopian, and the Oriental regions, are also generally admitted to be well

characterised by their terrestrial molluscs. There only remain the

Australian and the Neotropical regions, in which some want of homogeneity

is apparent, owing to the vast development and specialisation of certain

groups in the islands which belong to these regions. The Antilles, on the

one hand, and the Polynesian Islands, on the other, are so rich in

land-shells and possess so many peculiar forms, that, judged by these

alone, they must form primary instead of secondary divisions. We have,

however, already pointed out the inconvenience of any such partial systems

of zoological geography, and the causes have been sufficiently indicated

which have, in the case of land-shells as of insects, produced certain

special features of distribution.

We therefore venture to hope, that conchologists will give us the advantage

of their more full and accurate knowledge both of the classification and

distribution of this interesting group of animals, not to map out new sets

of regions for themselves, but to show what kind of barriers have been most

efficient in limiting the range of species, and how their distribution is

actually effected, so as to be able to explain whatever discrepancies exist

between the actual distribution of land-shells and that of the higher

animals.

_Order III.--OPISTHO-BRANCHIATA._

There are ten families in this order, all of which, as far as known, are

widely or universally distributed. Some of them are found fossil, ranging

back to the Carboniferous epoch. They are commonly termed Sea-slugs, and

have either a thin small shell or none. We shall therefore simply enumerate

the families, with the number of genera and species as given by Mr.

Woodward.

{530}FAMILY 31.--TORNATELLIDÆ. (7 Genera, 62 Species living, 166 fossil.)

FAMILY 32.--BULLIDÆ. (12 Genera, 168 Species living, 88 fossil.)

FAMILY 33.--APHYSIADÆ. (8 Genera, 84 Species living, 4 fossil.)

FAMILY 34.--PLEUROBRANCHIDÆ. (7 Genera, 28 Species living, 5 fossil.)

FAMILY 35.--PHYLLIDIADÆ. (4 Genera, 14 Species living, 0 fossil.)

FAMILY 36.--DORIDÆ. (23 Genera, 160 Species living, 0 fossil.)

FAMILY 37.--TRITONIADÆ. (9 Genera, 38 Species living, 0 fossil.)

FAMILY 38.--ÆOLIDÆ. (14 Genera, 101 Species living, 0 fossil.)

FAMILY 39.--PHYLLYRHOIDÆ. (1 Genus, 6 Species living, 0 fossil.)

FAMILY 40.--ELYSIADÆ. (5 Genera, 13 Species living, 0 fossil.)

{531}_Order IV.--NUCLEO-BRANCHIATA._

These are oceanic, swimming molluscs, of a delicate texture. They are found

in all warm seas, and range back to the Lower Silurian epoch. There are

only two families.

FAMILY 41.--FIROLIDÆ. (2 Genera, 33 Species living, 1 fossil.)

FAMILY 42.--ATLANTIDÆ. (5 Genera, 22 Species living, 159 fossil.)

CLASS.--PTEROPODA.

These are swimming, oceanic mollusca, inhabiting both Arctic, Temperate,

and Tropical seas. The three families have each a wide distribution in all

the great oceans. They range back to the Silurian period.

FAMILY 1.--HYALEIDÆ. (9 Genera, 52 Species living, 95 fossil.)

FAMILY 2.--LIMACINIDÆ. (4 Genera, 19 Species living, 0 fossil.)

FAMILY 3.--CLIONIDÆ. (4 Genera, 14 Species living, 0 fossil.)

{532}CLASS.--BRACHIOPODA.

These are sedentary, bivalve, marine mollusca, having laterally symmetrical

shells, but with unequal valves. Both in space and time they are the most

widely distributed molluscs. They are found in all seas, and at all depths;

and when any of the families or genera have a restricted range, it seems to

be due to our imperfect knowledge, rather than to any real geographical

limitations. In time they range back to the Cambrian formation, and seem to

have had their maximum development in the Silurian period. It is not,

therefore, necessary for our purpose, to do more than give the names of the

families with the numbers of the genera and species, as before.

FAMILY 1.--TEREBRATULIDÆ. (5 Genera, 67 Species living, 340 fossil.)

FAMILY 2.--SPIRIFERIDÆ. (4 Genera, 0 Species living, 380 fossil.)

FAMILY 3.--RHYNCHONELLIDÆ. (3 Genera, 4 Species living, 422 fossil.)

FAMILY 4.--ORTHIDÆ. (4 Genera, 0 Species living, 328 fossil.)

FAMILY 5.--PRODUCTIDÆ. (3 Genera, 0 Species living, 146 fossil.)

FAMILY 6.--CRANIADÆ. (1 Genus, 5 Species living, 37 fossil.)

FAMILY 7.--DISCINIDÆ. (2 Genera, 10 Species living, 90 fossil.)

FAMILY 8.--LINGULIDÆ. (2 Genera, 16 Species living, 99 fossil.)

{533}CLASS.--CONCHIFERA.

The Conchifera, or ordinary Bivalve Molluscs, may be distinguished from the

Brachiopoda by having their shells laterally unsymmetrical, while the

valves are generally (but not always) equal. They are mostly marine, but a

few inhabit fresh water. As the distribution of some of the families

presents points of interest, we shall treat them in the same manner as the

marine Gasteropoda.

FAMILY 1.--OSTREIDÆ. (5 Genera, 426 Species.)

DISTRIBUTION.--The Ostreidæ, including the Oysters and Scallops, are found

in all seas, Arctic as well as Tropical. There are nearly 1,400 species

fossil, ranging back to the Carboniferous period.

FAMILY 2.--AVICULIDÆ. (3 Genera, 94 Species.)

DISTRIBUTION.--The Aviculidæ, or Wing-shells and Pearl Oysters, are

characteristic of Tropical and warm seas, a few only ranging into temperate

regions. Nearly 700 fossil species are known from various formations

ranging back to the Devonian, and Lower Silurian.

FAMILY 3.--MYTILIDÆ. (3 Genera, 217 Species.)

DISTRIBUTION.--The Mytilidæ, or Mussels, have a world-wide distribution.

There is one fresh-water species, which inhabits the Volga. There are about

350 fossil species, ranging back to the Carboniferous epoch.

{534}FAMILY 4.--ARCADÆ. (6 Genera, 360 Species.)

DISTRIBUTION.--The Arcadæ are universally distributed, and are most

abundant in warm seas. The genus _Leda_ is, however, abundant in Arctic and

Temperate regions, and _Solenella_ is confined to the South Temperate zone.

There are near 1,200 fossil species, found in all strata as low as the

Lower Silurian.

FAMILY 5.--TRIGONIADÆ. (1 Genus, 3 Species.)

DISTRIBUTION.--The living _Trigoniæ_ are confined to Australia, but there

are 5 other genera fossil, containing about 150 species, and found in

various formations from the Chalk to the Lower Silurian.

FAMILY 6.--UNIONIDÆ. (7 Genera, 549 Species.)

DISTRIBUTION.--The Unionidæ, or Fresh-water Mussels, are found in all the

fresh waters of the globe, but some of the genera are restricted.

_Castalia_, _Mycetopus_ and _Mulleria_ are confined to the rivers of South

America; _Anodon_, to the Nearctic and Palæarctic regions; _Iridina_, and

_Etheria_, to the rivers of Africa; _Unio_ has a universal distribution,

but is especially abundant in North America. About 60 fossil species are

found in the Tertiary and Wealden formations.

FAMILY 7.--CHAMIDÆ. (1 Genus, 50 Species.)

DISTRIBUTION.--The Chamidæ, or Giant Clams, are confined to Tropical seas,

chiefly among coral reefs. There are two other genera and 62 species

fossil, ranging from the Chalk to the Oolite formations.

FAMILY 8.--HIPPURITIDÆ. (5 Genera, 103 Species.)

Fossils of doubtful affinity, from the Chalk formation.

{535}FAMILY 9.--TRIDACNIDÆ. (1 Genus, 8 Species.)

DISTRIBUTION.--The Tridacnidæ, or Clam-shells, are of very large size, and

are confined to the Tropical regions of the Indian and Pacific Oceans. A

few species have been found fossil in the Miocene formation.

FAMILY 10.--CARDIADÆ. (1 Genus, 200 Species.)

DISTRIBUTION.--The Cardiadæ, or Cockles, are of world-wide distribution.

Another genus is fossil, and nearly 400 fossil species are known, ranging

back to the Upper Silurian formation.

FAMILY 11.--LUCINIDÆ (8 Genera, 178 Species.)

DISTRIBUTION.--The Lucinidæ inhabit the Tropical and Temperate seas of all

parts of the world; but the genus _Corbis_ is confined to the Indian and

Pacific Oceans, _Montacuta_ and _Lepton_, to the Atlantic. There are nearly

500 extinct species, ranging from the Tertiary back to the Silurian

formation.

FAMILY 12.--CYCLADIDÆ. (3 Genera, 176 Species.)

DISTRIBUTION.--The Cycladidæ are small fresh- or brackish-water shells

found all over the globe. The genus _Cyclas_ is most abundant in the North

Temperate zone, while _Cyrena_ inhabits the warmer shores of the Atlantic

and Pacific, but is absent from the West Coast of America. There are about

150 species fossil, ranging back from the Pliocene to the Wealden

formations.

FAMILY 13.--CYPRINIDÆ. (10 Genera, 176 Species).

DISTRIBUTION.--Universal. _Cyprina_ and _Astarte_ are Arctic and North

Temperate; _Cardita_ is Tropical and South Temperate. There are several

extinct genera and about 1,000 species found in all formations as far back

as the Lower Silurian.

{536}FAMILY 14.--VENERIDÆ. (10 Genera, 600 Species.)

DISTRIBUTION.--Universal. _Lucinopsis_ is confined to the North Atlantic;

_Glauconeza_ to the months of rivers in the Oriental region; _Meroe_ and

_Trigona_ to warm seas. There are about 350 fossil species, ranging back to

the Oolitic period.

FAMILY 15.--MACTRIDÆ. (5 Genera, 147 Species.)

DISTRIBUTION.--All seas, but more abundant in the Tropics. _Gnathodon_ is

found in the Gulf of Mexico; _Anatinella_ in the Oriental region. There are

about 60 fossil species, ranging back to the Carboniferous period.

FAMILY 16.--TELLINIDÆ. (11 Genera, 560 Species.)

DISTRIBUTION.--All seas; most abundant in the Tropics. _Galatea_ is

confined to African rivers. There are about 60 fossil species, mostly

Tertiary, but ranging back to the Carboniferous period.

FAMILY 17.--SOLENIDÆ. (3 Genera, 63 Species.)

DISTRIBUTION.--All Temperate and Tropical seas. There are 80 fossil species

which range back to the Carboniferous epoch.

FAMILY 18.--MYACIDÆ. (6 Genera, 121 Species.)

DISTRIBUTION.--All seas. _Panopæa_ inhabits both North and South Temperate

seas; _Glycimeris_, Arctic seas. There are near 350 fossil species, ranging

back to the Lower Oolite formation.

FAMILY 19.--ANATINIDÆ. (8 Genera, 246 Species.)

DISTRIBUTION.--All seas. _Pholadomya_ is from Tropical Africa; _Myadora_

from the Western Pacific; _Myochama_ and _Chamostræa_ are Australian. There

are about 400 fossil species, ranging back to the Lower Silurian formation.

{537}FAMILY 20.--GASTROCHÆNIDÆ. (5 Genera, 40 Species.)

DISTRIBUTION.--Temperate and warm seas. _Aspergillum_ ranges from the Red

Sea to New Zealand. There are 35 fossil species, ranging back to the Lower

Oolite.

FAMILY 21.--PHOLADIDÆ (4 Genera, 81 Species.)

DISTRIBUTION.--These burrowing molluscs inhabit all Temperate and warm seas

from Norway to New Zealand. There are about 50 fossil species, ranging back

to the epoch of the Lias.

_General Remarks on the Distribution of the Marine Mollusca._

The marine Mollusca are remarkable for their usually wide distribution.

About 48 of the families are cosmopolitan, ranging over both hemispheres,

and in cold as well as warm seas. About 15 are restricted to the warmer

seas of the globe; but several of these extend from Norway to New Zealand,

a distribution which may be called universal, and only 2 or 3 are

absolutely confined to Tropical seas. Two small families only, are confined

to the Pacific and Indian Oceans. Marine fishes, on the other hand, have a

much less cosmopolitan character, no less than 30 families having a limited

distribution, while 50 are universal. Some of these 30 families are

confined to the Northern seas, some to the Atlantic and Mediterranean, and

a considerable number to the Indian Ocean and Western Pacific. Many of

these families, it is true, are much smaller than those of the Mollusca,

which seem to possess very few of those small isolated families of two or

three species only, which abound in all the Vertebrate classes. These

differences are no doubt connected with the higher organisation of fishes,

which renders them more susceptible to changed conditions of life; and this

is indicated by the much less antiquity of existing families of fishes, the

greater part of which do not date back beyond the Cretaceous epoch, and

many of them only to the Eocene. In striking contrast we have the vast

antiquity of most of the families of {538}Mollusca, as shown in the

following table of their range taken from Mr. Woodward's work, but

re-arranged, and somewhat modified.

1 = Lower Silurian. 6 = Trias. 11 = Eocene.

2 = Upper Silurian. 7 = Lower Oolite. 12 = Miocene.

3 = Devonian. 8 = Upper Oolite. 13 = Pliocene.

4 = Carboniferous. 9 = Lower Cretaceous. 14 = Recent.

5 = Permian. 10 = Upper Cretaceous.

+-----------------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

| and disappearance. | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|12|13|14|

+-----------------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

| Productidæ |--|--|--|--|--| | | | | | | | | |

| Orthoceratidæ |--|--|--|--|--|--| | | | | | | | |

| Spiriferidæ, Orthidæ |--|--|--|--|--|--|--| | | | | | | |

| Atlantidæ, Hyaleidæ |--|--|--|--|--|--|--|--|--|--|--|--|--|--|

| Pyramidellidæ, Turbinidæ |--|--|--|--|--|--|--|--|--|--|--|--|--|--|

| Ianthidæ, Chitonidæ |--|--|--|--|--|--|--|--|--|--|--|--|--|--|

| Lingulidæ |--|--|--|--|--|--|--|--|--|--|--|--|--|--|

| Aviculidæ, Mytilidæ |--|--|--|--|--|--|--|--|--|--|--|--|--|--|

| Arcadæ, Trigoniadæ |--|--|--|--|--|--|--|--|--|--|--|--|--|--|

| Cyprinidæ, Anatinidæ |--|--|--|--|--|--|--|--|--|--|--|--|--|--|

| Nautilidæ | |--|--|--|--|--|--|--|--|--|--|--|--|--|

| Rhynchonellidæ, Craniadæ, } | | | | | | | | | | | | | | |

| Discinidæ } | |--|--|--|--|--|--|--|--|--|--|--|--|--|

| Cardiadæ, Lucinidæ | |--|--|--|--|--|--|--|--|--|--|--|--|--|

| Ammonitidæ | | |--|--|--|--|--|--|--|--| | | | |

| Naticidæ, Calyptræidæ | | |--|--|--|--|--|--|--|--|--|--|--|--|

| Dentalidæ, Terebratulidæ | | |--|--|--|--|--|--|--|--|--|--|--|--|

| Helicidæ | | | |--| | | | | | |--|--|--|--|

| Fissurellidæ, Tornatellidæ | | | |--|--|--|--|--|--|--|--|--|--|--|

| Pectinidæ, Solenidæ | | | |--|--|--|--|--|--|--|--|--|--|--|

| Cerithiadæ, Littorinidæ, } | | | | | | | | | | | | | | |

| Astartidæ } | | | | | |--|--|--|--|--|--|--|--|--|

| Belemnitidæ | | | | | | |--|--|--|--| | | | |

| Teuthidæ, Sepiadæ | | | | | | |--|--|--|--|--|--|--|--|

| Neritidæ, Patellidæ, } | | | | | | | | | | | | | | |

| Bullidæ } | | | | | | |--|--|--|--|--|--|--|--|

| Gastrochænidæ, Pholadidæ | | | | | | |--|--|--|--|--|--|--|--|

| Limnæidæ, Melaniadæ | | | | | | | |--|--|--|--|--|--|--|

| Chamidæ, Myadæ | | | | | | | |--|--|--|--|--|--|--|

| Cycladidæ, Veneridæ, } | | | | | | | | | | | | | | |

| Tellinidæ } | | | | | | | |--|--|--|--|--|--|--|

| Hippuritidæ | | | | | | | | |--|--| | | | |

| Unionidæ | | | | | | | | |--|--|--|--|--|--|

| Strombidæ, Buccinidæ | | | | | | | | |--|--|--|--|--|--|

| Conidæ, Volutidæ | | | | | | | | |--|--|--|--|--|--|

| Auriculidæ, Cyclostomidæ | | | | | | | | |--|--|--|--|--|--|

| Mactridæ | | | | | | | | |--|--|--|--|--|--|

| Limacidæ | | | | | | | | | | |--|--|--|--|

| Argonautidæ | | | | | | | | | | | | |--|--|

| Tridacnidæ | | | | | | | | | | | | |--|--|

+-----------------------------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

Nor is this enormous antiquity confined to family types alone. Many genera

are equally ancient. The genus _Lingula_ has {539}existed from the earliest

Palæozoic times down to the present day; while _Terebratula_,

_Rhynchonella_, _Discina_, _Nautilus_, _Natica_, _Pleurotomaria_,

_Patella_, _Dentalium_, _Mytilus_ and many other living forms, range back

to the Palæozoic epoch. That groups of such immense antiquity, and having

power to resist such vast changes of external conditions as they must have

been subject to, should now be widely distributed, is no more than might

reasonably be expected. It is only in the case of sub-genera and species,

that we can expect the influence of recent geological or climatal changes

to be manifest; and it must be left to special students to work out the

details of their distribution, with reference to the general principles

found to obtain among the more highly organised animals.

{540}CHAPTER XXIII.

SUMMARY OF THE DISTRIBUTION, AND LINES OF MIGRATION, OF THE SEVERAL CLASSES

OF ANIMALS.

Having already given summaries of the distribution of the several orders,

and of some of the classes of land animals, we propose here to make a few

general remarks on the special phenomena presented by the more important

groups, and to indicate where possible, the general lines of migration by

which they have become dispersed over wide areas.

MAMMALIA.

This class is very important, and its past history is much better known

than that of most others. We shall therefore briefly summarise the results

we have arrived at from our examination of the distribution of extinct and

living forms of each order.

_Primates._--This order, being pre-eminently a tropical one, became

separated into two portions, inhabiting the Eastern and Western Hemispheres

respectively, at a very early epoch. In consequence of this separation it

has diverged more radically than most other orders, so that the two

American families, Cebidæ and Hapalidæ, are widely differentiated from the

Apes, Monkeys, and Lemurs of the Old World. The Lemurs were probably still

more ancient, but being much lower in organisation, they became extinct in

most of the areas where the higher forms of Primates became developed.

Remains found in the Eocene formation indicate, that the North American and

European {541}Primates had, even at that early epoch, diverged into

distinct series, so that we must probably look back to the secondary period

for the ancestral form from which the entire order was developed.

_Chiroptera._--These are also undoubtedly very ancient. The most

generalised forms--the Vespertilionidæ and Noctilionidæ--are the most

widely distributed; while special types have arisen in America, and in the

Eastern Hemisphere. Remains found in the Upper Eocene formation of Europe

differ little from species still living in the same countries; so that we

can form no conjecture as to the origin or migration, of the group. Their

power of flight would, however, enable them rapidly to spread over all the

great continents of the globe.

_Insectivora._--This very ancient group, now probably verging towards

extinction, appears to have originated in the Northern continent, and never

to have reached Australia or South America. It may, however, have become

extinct in the latter country owing to the competition of the numerous

Edentata. The Insectivora now often maintain themselves amidst more highly

developed forms, by means of some special protection. Some burrow in the

earth,--like the moles; others have a spiny covering,--as the hedgehog's

and several of the Centetidæ; others are aquatic,---as the _Potamogale_ and

the desman; others have a nauseous odour,--as the shrews; while there are

several which seem to be preserved by their resemblance to higher

forms,--as the elephant-shrews to jerboas, and the tupaias to squirrels.

The same need of protection is shown by the numerous Insectivora inhabiting

Madagascar, where the competing forms are few; and by one lingering in the

Antilles, where there are hardly any other mammalia.

_Carnivora._--Although perhaps less ancient than the preceding, this form

of mammal is far more highly organised, and from its earliest appearance

appears to have become dominant in the world. It would therefore soon

spread widely, and diverge into the various specialised types represented

by existing families. Most of these appear to have originated in the

Eastern Hemisphere, the only Carnivora occurring in North {542}American

Miocene deposits being ancestral forms of Canidæ and Felidæ. It seems

probable, therefore, that the order had attained a considerable development

before it reached the Western Hemisphere. The Procyonidæ, now confined to

America, are not very ancient; and the occurrence of a few allied forms in

the Himalayas (_Ælurus_ and _Æluropus_) render it probable that their

common ancestors entered North America from the Palæarctic region during

the Miocene period, but being a rather low type they have succumbed under

the competition of higher forms in most parts of the Eastern Hemisphere.

Bears and Weasels are probably still more recent emigrants to America. The

aquatic carnivora (Seals, &c.) are, as might be expected, more widely and

uniformly distributed, but there is little evidence to show at what period

the type was first developed.

_Ungulata._--These are the dominant vegetable-feeders of the great

continents, and they have steadily increased in numbers and in

specialisation from the oldest Tertiary times to the present day. Being

generally of larger size and less active than the Carnivora, they have

somewhat more restricted powers of dispersal. We have good evidence that

their wide range over the globe is a comparatively recent phenomenon.

Tapirs and Llamas have probably not long inhabited South America, while

Rhinoceroses and Antelopes were once, perhaps, unknown in Africa, although

abounding in Europe and Asia. Swine are one of the most ancient types in

both hemispheres; and their great hardiness, their omnivorous diet, and

their powers of swimming, have led to their wide distribution. The sheep

and goats, on the other hand, are perhaps the most recent development of

the Ungulata, and they seem to have arisen in the Palæarctic region at a

time when its climate already approximated to that which now prevails.

Hence they are pre-eminently a Temperate group, never found within the

Tropics except upon a few mountain ranges.

_Proboscidea._--These huge animals (the Elephants and Mastodons) appear to

have originated in the warmer parts of the Palæarctic region, but they soon

spread over all the great {543}continents, even reaching the southern

extremity of America. Their extinction has probably depended more on

physical than on organic changes, and we can clearly trace their almost

total disappearance to the effects of the Glacial epoch.

_Rodentia._--Rodents are a very dominant group, and a very ancient one.

Owing to their small size and rapid powers of increase, they soon spread

over almost every part of the globe, whence has resulted a great

specialisation of family types in the South American continent which

remained so long isolated. They are capable of living wherever there is any

kind of vegetable food, hence their range will be determined rather by

organic than by physical conditions; and the occupation of a country by

enemies or by competing forms, is probably the chief cause which has

prevented many of the families from acquiring a wide range. The occurrence

of isolated species of the South American families, Octodontidæ and

Echimyidæ in the Ethiopian and Palæarctic regions, is an indication that

the range of many of the families has recently become less extensive.

_Edentata._--These singular and lowly-organised animals appear to have

become almost restricted to the two great Southern lands--South Africa and

South America--at an early period; and, being there free from the

competition of higher forms, developed a number of remarkable types often

of huge size, of which the Megatherium is one of the best known. The

incursion of the highly-organised Ungulates and Carnivora into Africa

during the Miocene epoch, probably exterminated most of them in that

continent; but in America they continued in full force down to the

Post-Pliocene period; and even now, the comparatively diminutive Sloths,

Ant-eaters, and Armadillos, form a large and important portion of the

fauna.

_Marsupialia and Monotremata._--These are probably the representatives of

the most ancient and lowly-organised types of mammal. They once existed in

the northern continents, whence they spread into Australia; and being

isolated, and preserved from the competition of the higher forms which soon

arose in other parts of the world, they have developed into a variety of

types, which, however, still preserve a general {544}uniformity of

organisation. One family, which continued to exist in Europe till the

latter part of the Miocene period, reached America, and has there been

preserved to our day.

_Lines of Migration of the Mammalia._--The whole series of phenomena

presented by the distribution of the Mammalia, looked at broadly, are in

harmony with the view that the great continents and oceans of our own epoch

have been in existence, with comparatively small changes, during all

Tertiary times. Each one of them has, no doubt, undergone considerable

modifications in its area, its altitude, and in its connection with other

lands. Yet some considerable portion of each continent has, probably, long

existed in its present position, while the great oceans seem to have

occupied the same depressions of the earth's crust (varied, perhaps, by

local elevations and subsidences) during all this vast period of time.

Hence, allowing for the changes of which we have more or less satisfactory

evidence, the migrations of the chief mammalian types can be pretty clearly

traced. Some, owing to their small size and great vitality, have spread to

almost all the chief land masses; but the majority of the orders have a

more restricted range. All the evidence at our command points to the

Northern Hemisphere as the birth-place of the class, and probably of all

the orders. At a very early period the land communication with Australia

was cut off, and has never been renewed; so that we have here preserved for

us a sample of one or more of the most ancient forms of mammal. Somewhat

later the union with South America and South Africa was severed; and in

both these countries we have samples of a somewhat more advanced stage of

mammalian development. Later still, the union by a northern route between

the Eastern and Western Hemispheres appears to have been broken, partly by

a physical separation, but almost as effectually by a lowering of

temperature. About the same period the separation of the Palæarctic region

from the Oriental was effected, by the rise of the Himalayas and the

increasing contrast of climate; while the formation of the great

desert-belts of the Sahara, Arabia, Persia, and Central Asia, helped to

complete the separation of {545}the Temperate and Tropical zones, and to

render further intermigration almost impossible.

In a few cases--of which the Rodents in Australia and the pigs in

Austro-Malaya are perhaps the most striking examples--the distribution of

land-mammals has been effected by a sea-passage either by swimming or on

floating vegetation; but, as a rule, we may be sure that the migrations of

mammalia have taken place over the land; and their presence on islands is,

therefore, a clear indication that these have been once connected with a

continent. The present class of animals thus affords the best evidence of

the past history of the land surface of our globe; and we have chiefly

relied upon it in sketching out (in Part III.) the probable changes which

each of our great regions has undergone.

_Birds._

Although birds are, of all land-vertebrates, the best able to cross seas

and oceans, it is remarkable how closely the main features of their

distribution correspond with those of the Mammalia. South America possesses

the low Formicaroid type of Passeres,--which, compared with the more highly

developed forms of the Eastern Hemisphere, is analogous to the Cebidæ and

Hapalidæ as compared with the Old World Apes and Monkeys; while its Cracidæ

as compared with the Pheasants and Grouse, may be considered parallel to

the Edentata as compared with the Ungulates of the Old World. The

Marsupials of America and Australia, are paralleled among birds, in the

Struthionidæ and Megapodiidæ; the Lemurs and Insectivora preserved in

Madagascar are represented by the Mascarene Dididæ; the absence of Deer and

Bears from Africa is analogous to the absence of Wrens, Creepers, and

Pheasants; while the African Hyracidæ and Chrysochloridæ among mammals, may

well be compared with the equally peculiar Coliidæ and Musophagidæ among

birds.

From these and many other similarities of distribution, it is clear that

birds have, as a rule, followed the same great lines of migration as

mammalia; and that oceans, seas, and deserts, have {546}always to a great

extent limited their range. Yet these barriers have not been absolute; and

in the course of ages birds have been able to reach almost every habitable

land upon the globe. Hence have arisen some of the most curious and

interesting phenomena of distribution; and many islands, which are entirely

destitute of mammalia, or possess a very few species, abound in birds,

often of peculiar types and remarkable for some unusual character or habit.

Striking examples of such interesting bird-faunas are those of New Zealand,

the Sandwich Islands, the Galapagos, the Mascarene Islands, the Moluccas,

and the Antilles; while even small and remote islets,--such as Juan

Fernandez and Norfolk Island, have more light thrown upon their past

history by means of their birds, than by any other portion of their scanty

fauna.

Another peculiar feature in the distribution of this class is the

extraordinary manner in which certain groups and certain external

characteristics, have become developed in islands, where the smaller and

less powerful birds have been protected from the incursions of mammalian

enemies, and where rapacious birds--which seem to some degree dependent on

the abundance of mammalia--are also scarce. Thus, we have the Pigeons and

the Parrots most wonderfully developed in the Australian region, which is

pre-eminently insular; and both these groups here acquire conspicuous

colours very unusual, or altogether absent, elsewhere. Similar colours

(black and red) appear, in the same two groups, in the distant Mascarene

islands; while in the Antilles the parrots have often white heads, a

character not found in the allied species on the South American continent.

Crests, too, are largely developed, in both these groups, in the Australian

region only; and a crested parrot formerly lived in Mauritius,--a

coincidence too much like that of the colours as above noted, to be

considered accidental.

Again, birds exhibit to us a remarkable contrast as regards the oceanic

islands of tropical and temperate latitudes; for while most of the former

present hardly any cases of specific identity with the birds of adjacent

continents, the latter often show hardly any differences. The Galapagos and

Madagascar {547}are examples of the first-named peculiarity; the Azores and

the Bermudas of the last; and the difference can be clearly traced to the

frequency and violence of storms in the one case and to the calms or steady

breezes in the other.

It appears then, that although birds do not afford us the same convincing

proof of the former union of now disjoined lands as we obtain from mammals,

yet they give us much curious and suggestive information as to the various

and complex modes in which the existing peculiarities of the distribution

of animals have been brought about. They also throw much light on the

relation between distribution and the external characters of animals; and,

as they are often found where mammalia are quite absent, we must rank them

as of equal value for the purposes of our present study.

_Reptiles._

These hold a somewhat intermediate place, as regards their distribution,

between mammals and birds, having on the whole rather a wider range than

the former, and a more restricted one than the latter.

Snakes appear to have hardly more facilities for crossing the ocean than

mammals; hence they are generally absent from oceanic islands. They are

more especially a tropical group, and have thus never been able to pass

from one continent to another by those high northern and southern routes,

which we have seen reason to believe were very effectual in the case of

mammalia and some other animals. Hence we find no resemblance between the

Australian and Neotropical regions, or between the Palæarctic and Nearctic;

while the Western Hemisphere is comparatively poor as regards variety of

types, although rich in genera and species. Deserts and high mountains are

also very effectual barriers for this group, and their lines of migration

have probably been along river valleys, and occasionally across narrow seas

by means of floating vegetation.

Lizards, being somewhat less tropical than snakes, may have passed by the

northern route during warm epochs. They are also more suited to traverse

deserts, and they possess some unknown {548}means of crossing the ocean, as

they are not unfrequently found in remote oceanic islands. These various

causes have modified their distribution. The Western Hemisphere is much

richer in lizards than it is in snakes; and it is also very distinct from

the Eastern Hemisphere. The lines of migration of lizards appear to have

been along the mountains and deserts of tropical countries, and, under

special conditions, across tropical seas from island to island.

Crocodiles are a declining group. They were once more generally

distributed, all the three families being found in British Eocene deposits.

Being aquatic and capable of living in the sea, they can readily pass along

all the coasts and islands of the warmer parts of the globe. Tortoises are

equally ancient, and the restriction of certain groups to definite areas

seems to be also a recent phenomenon.

_Amphibia._

The Amphibia differ widely from Reptiles in their power of enduring cold;

one of their chief divisions, the Urodela or Tailed-Batrachia, being

confined to the temperate parts of the Northern Hemisphere. To this class

of animals the northern and southern routes of migration were open; and we

accordingly find a considerable amount of resemblance between South America

and Australia, and a still stronger affinity between North America and the

Palæarctic continent. The other tropical regions are more distinct from

each other; clearly indicating that, in this group, it is tropical deserts

and tropical oceans which are the barriers to migration. The class however

is very fragmentary, and probably very ancient; so that descendants of once

widespread types are now found isolated in various parts of the globe,

between which we may feel sure there has been no direct transmission of

Batrachia. Remembering that their chief lines of migration have been by

northern and southern land-routes, by floating ice, by fresh-water

channels, and perhaps at rare intervals by ova being carried by aquatic

birds or by violent storms,--we shall be able to comprehend most of the

features of their actual distribution.

{549}_Fresh-water Fishes._

Although it would appear, at first sight, that the means of dispersal of

these animals are very limited, yet they share to some extent the wide

range of other fresh-water organisms. They are found in all climates; but

the tropical regions are by far the most productive, and of these South

America is perhaps the richest and most peculiar. There is a certain amount

of identity between the two northern continents, and also between those of

the South Temperate zone; yet all are radically distinct, even North

America and Europe having but a small proportion of their forms in common.

The occurrence of allied fresh-water species in remote lands--as the

_Aphritis_ of Tasmania and Patagonia, and the _Comephorus_ of Lake Baikal,

distantly allied to the mackerels of Northern seas--would imply that marine

fishes are often modified for a life in fresh waters; while other facts no

less plainly show that permanent fresh-water species are sometimes

dispersed in various ways across the oceans, more especially by the

northern and southern routes.

The families of fresh-water fishes are often of restricted range, although

cases of very wide and scattered distribution also occur. The great

zoological regions are, on the whole, very well characterized; showing that

the same barriers are effectual here, as with most other vertebrates. We

conclude, therefore, that the chief lines of migration of fresh-water

fishes have been across the Arctic and Antarctic seas, probably by means of

floating ice as well as by the help of the vast flocks of migratory aquatic

birds that frequent those regions. On continents they are, usually, widely

dispersed; but tropical seas, even when of small extent, appear to have

offered an effectual barrier to their dispersal. The cases of affinity

between Tropical America, Africa, Asia, and Australia, must therefore be

imputed either to the survival of once widespread groups, or to analogous

adaptation to a fresh-water life of wide-spread marine types; and these

cases cannot be taken as evidence of any former land connection between

such remote continents.

{550}_Insects._

It has already been shown (Vol. I. pp. 209-213 and Vol. II. pp. 44-48) that

the peculiarities of distribution of the various groups of insects depend

very much on their habits and general economy. Their antiquity is so vast,

and their more important modifications of structure have probably occurred

so slowly, that modes of dispersal depending on such a combination of

favourable conditions as to be of excessive rarity, may yet have had time

to produce large cumulative effects. Their small specific gravity and their

habits of flight render them liable to dispersal by winds to an extent

unknown in other classes of animals; and thus, what are usually very

effectual barriers have been overstepped, and sometimes almost obliterated,

in the case of insects. A careful examination will, however, almost always

show traces of an ancient fauna, agreeing in character with other classes

of animals, intermixed with the more prominent and often more numerous

forms whose presence is due to this unusual facility of dispersal.

The effectual migration of insects is, perhaps more than in any other class

of animals, limited by organic and physical conditions. The vegetation, the

soil, the temperature, and the supply of moisture, must all be suited to

their habits and economy; while they require an immunity from enemies of

various kinds, which immigrants to a new country seldom obtain. Few

organisms have, in so many complex ways, become adapted to their special

environment, as have insects. They are in each country more or less adapted

to the plants which belong to it; while their colours, their habits, and

the very nature of the juices of their system, are all modified so as to

protect them from the special dangers which surround them in their native

land. It follows, that while no animals are so well adapted to show us the

various modes by which dispersal may be effected, none can so effectually

teach us the true nature and vast influence of the organic barrier in

limiting dispersal.

It is probable that insects have at one time or another taken advantage of

every line of migration by which any terrestrial {551}organisms have spread

over the earth, but owing to their small size and rapid multiplication,

they have made use of some which are exclusively their own. Such are the

passage along mountain ranges from the Arctic to the Antarctic regions, and

the dispersal of certain types over all temperate lands. It will perhaps be

found that insects have spread over the land surface in directions

dependent on our surface zones--forests, pastures, and deserts;--and a

study of these, with a due consideration of the fact that narrow seas are

scarcely a barrier to most of the groups, may assist us to understand many

of the details of insect-distribution.

_Terrestrial Mollusca._

The distribution of land-shells agrees, in some features, with that of

insects, while in others the two are strongly contrasted. In both we see

the effects of great antiquity, with some special means of dispersal; but

while in insects the general powers of motion, both voluntary and

involuntary, are at a maximum, in land-molluscs they are almost at a

minimum. Although to some extent dependent on vegetation and climate, the

latter are more dependent on inorganic conditions, and also to a large

extent on the general organic environment. The result of these various

causes, acting through countless ages, has been to spread the main types of

structure with considerable uniformity over the globe; while generic and

sub-generic forms are often wonderfully localized.

Land-shells, even more than insects, seem, at first sight, to require

regions of their own; but we have already pointed out the disadvantages of

such a method of study. It will be far more instructive to refer them to

those regions and sub-regions which are found to accord best with the

distribution of the higher animals, and to consider the various anomalies

they present as so many problems, to be solved by a careful study of their

habits and economy, and especially by a search after the hidden causes

which have enabled them to spread so widely over land and ocean.

The lines of migration which land-shells have followed, can {552}hardly be

determined with any definiteness. On continents they seem to spread

steadily, but slowly, in every direction, checked probably by organic and

physical conditions rather than by the barriers which limit the higher

groups. Over the ocean they are also slowly dispersed, by some means which

act perhaps at very long intervals, but which, within the period of the

duration of genera and families, are tolerably effective. It thus happens

that, although the powers of dispersal of land-shells and insects are so

very unequal, the resulting geographical distribution is almost the

opposite of what might have been expected,--the former being, on the whole,

less distinctly localized than the latter.

CONCLUSION.

The preceding remarks are all I now venture to offer, on the distinguishing

features of the various groups of land-animals as regards their

distribution and migrations. They are at best but indications of the

various lines of research opened up to us by the study of animals from the

geographical point of view, and by looking upon their range in space and

time as an important portion of the earth's history. Much work has yet to

be done before the materials will exist for a complete treatment of the

subject in all its branches; and it is the author's hope that his volumes

may lead to a more systematic collection and arrangement of the necessary

facts. At present all public museums and private collections are arranged

zoologically. All treatises, monographs, and catalogues, also follow, more

or less completely, the zoological arrangement; and the greatest difficulty

the student of geographical distribution has to contend against, is the

total absence of geographical collections, and the almost total want of

complete and comparable local catalogues. Till every well-marked

district,--every archipelago, and every important island, has all its known

species of the more important groups of animals catalogued on a uniform

plan, and with a uniform nomenclature, a thoroughly satisfactory account of

the Geographical Distribution of Animals will not be possible. But more

than this is wanted. Many of the most curious relations between animal

{553}forms and their habitats, are entirely unnoticed, owing to the

productions of the same locality _never_ being associated in our museums

and collections. A few such relations have been brought to light by modern

scientific travellers, but many more remain to be discovered; and there is

probably no fresher and more productive field still unexplored in Natural

History. Most of these curious and suggestive relations are to be found in

the productions of islands, as compared with each other, or with the

continents of which they form appendages; but these can never be properly

studied, or even discovered, unless they are visibly grouped together. When

the birds, the more conspicuous families of insects, and the land-shells of

islands, are kept together so as to be readily compared with similar

associations from the adjacent continents or other islands, it is believed

that in almost every case there will be found to be peculiarities of form

or colour running through widely different groups, and strictly indicative

of local or geographical influences. Some of these coincident variations

have been alluded to in various parts of this work, but they have never

been systematically investigated. They constitute an unworked mine of

wealth for the enterprising explorer; and they may not improbably lead to

the discovery of some of the hidden laws (supplementary to Natural

Selection), which seem to be required, in order to account for many of the

external characteristics of animals.

In concluding his task, the author ventures to suggest, that naturalists

who are disposed to turn aside from the beaten track of research, may find

in the line of study here suggested a new and interesting pursuit, not

inferior in attractions to the lofty heights of transcendental anatomy, or

the bewildering mazes of modern classification. And it is a study which

will surely lead them to an increased appreciation of the beauty and the

harmony of nature, and to a fuller comprehension of the complex relations

and mutual interdependence, which link together every animal and vegetable

form, with the ever-changing earth which supports them, into one grand

organic whole.

{557}GENERAL INDEX.

All names in Italics refer, either to the genera and other groups of

Extinct Animals in Part II. of the First Volume;--or to the genera whose

distribution is given under Geographical Zoology (Part IV.) in the Second

Volume; the Families and higher groups being in small capitals. All other

references are in ordinary type.

The various matters discussed under Zoological Geography (Part III.), are

indexed as much as possible by subjects and localities. None of the genera

mentioned in this Part are indexed, as this would have more than doubled

the extent of the Index, and would have served no useful purpose, because

the general distribution of each genus is given in Part IV., and the

separate details can always be found by referring to the region,

sub-region, and class.

Aard-vark of East Africa, figure of, i. 261

Aard-vark, ii. 246

Aard-wolf, ii. 196

_Abacetus_, ii. 491

_Abax_, ii. 489

_Abisara_, ii. 475

_Ablabes_, ii. 375

_Ablepharus_, ii. 395

_Abramis_, ii. 453

_Abronia_, ii. 392

_Abrornis_, ii. 258

_Abrostomus_, ii. 451

_Aburria_, ii. 343

_Acalyptus_, ii. 384

_Acanthias_, ii. 401

_Acanthicus_, ii. 444

_Acanthion_, ii. 240

_Acanthis_, ii. 283

_Acanthisitta_, ii. 265

_Acanthiza_, ii. 258

_Acanthobrama_, ii. 453

ACANTHOCLINIDÆ, ii. 432

_Acanthodactylus_, ii. 391

_Acanthodelphis_, ii. 209

_Acantholabrus_, ii. 437

_Acanthomys_, ii. 229

_Acanthophis_, ii. 383

_Acanthopsis_, ii. 453

ACANTHOPTERYGII, ii. 424

ACANTHOPTERYGII PHARYNCOGNATHI, ii. 437

_Acanthopthalmus_, ii. 453

_Acanthoptila_, ii. 261

_Acanthopyga_, ii. 390

_Acanthorhynchus_, ii. 275

_Acanthosaura_, ii. 402

_Acara_, ii. 438

Accentor, ii. 260

Accentorinæ, ii. 257

_Accipenser_, ii. 459

ACCIPENSERIDÆ, ii. 459

_Accipiter_, ii. 348

_Accipitres_, European Eocene, i. 163

The Geographical Distribution of Animals, Volume 2 With a study of the relations of living and extinct faunas as elucidating the past changes of the Earth's surface · 第 14 / 18 章

_Fossil Fishes._--Fishes have existed from a very remote era, and it is