[Illustration]

FIG. 229.--Cape Sea-Lion. _Otaria pusilla._ x 1/16.

FAM. 1. OTARIIDAE.--The family Otariidae[320] is no doubt the least

modified of the aquatic Carnivora. It is rational, therefore, to commence

the survey of the group with this family. They have preserved, as already

noted, the independence of the hind-limbs; the external ear is present,

though small; there is an obvious neck, and the nostrils are at the end of

the snout, as in terrestrial creatures generally. The nails are small and

rudimentary, save those upon the three middle digits of the foot. It is a

singular fact that among the Otaries the angle of the lower jaw is

"inflected as much as in any Marsupial." The literature relating to this

family is great, and it seems difficult to reconcile the very varying

opinions as to how many genera ought to be admitted. Mr. Allen arranged the

nine species which he allowed {451} in six genera; but more generic names

have been proposed. At the other extreme stands Dr. Mivart, who speaks of

only one genus, _Otaria_; of this genus the number of species is by no

means agreed upon. There can, however, be no doubt of the distinctness of

the Northern Fur Seal, _O. ursina_ (the "Seal" of commerce and the cause of

international complications), of the Patagonian Maned Sea-Lion, _O.

jubata_,[321] of _O. pusilla_ of the Cape, of the Californian _O.

gillespiei_, of _O. hookeri_ from the Auckland Islands, and of four or five

others. The range of the genus is wide, but is mainly Antarctic. It is

usual to speak of "Hair Seals" and "Fur Seals," the latter being the

species which produce the "sealskin" of commerce. The difference is that in

the Fur Seals there is a dense, soft under-fur, which is wanting in the

other group. It is, however, impossible to make this character the basis of

a generic subdivision. There is a Fur Seal, _O. nigrescens_, in South

America as well as the more widely-known northern form.

FAM. 2. TRICHECHIDAE.--This family contains but one genus, _Trichechus_,

the Walrus or Morse, or _Odobaenus_, as the more correct term seems to be.

It is a tiresome result of accurate conformity with the rules of priority

in nomenclature that the name _Trichechus_ should be applied to the

Manatee. There is but one species of Walrus, though it has been attempted

to show that the Pacific and Eastern forms are different. The animal is

Arctic and circumpolar. The Walrus is characterised by the enormous canines

of its upper jaw, which form the well-known tusks and reach a length of 30

inches. The animal can progress on land like the Sea-Lions; but, as in the

Seals, there are no external ears, though there is a slight protuberance

above the meatus auditorius. The strong bristles upon the upper lip are as

thick as crow quills. The pectoral limb has nails, but these are small, as

in the Sea-Lions. The under surface of the manus has a warty pad, which

cannot but assist[322] in maintaining a foothold upon slippery ice. The

hind-limbs have longer nails, which are still diminutive and subequal in

size. There is no free tail. The liver of this animal is much furrowed, but

not so much so as in _Otaria_, though more so than in _Phoca_. The kidneys

are of course lobulate, as in the other aquatic Carnivores. The milk dental

formula appears to be I 3/3 C 1/1 Pm + M 5/4. In the adult the formula[323]

is I 1/0 C 1/1 M 3/3.

{452}

[Illustration]

FIG. 230.--Common Seal. _Phoca vitulina._ x 1/8. (From Parker and Haswell's

_Zoology_.)

FAM. 3. PHOCIDAE.--The true Seals have no external ears, and the nostrils

are quite dorsal in position as in other aquatic animals, such as the

Crocodile. There is obviously an approach to the conditions characteristic

of the Whales. The hind-limbs are useless for locomotion on land. They are

bound up with the tail, and form functionally merely a part of the tail. In

this family there are, at any rate, eight genera.

_Phoca_ and _Halichoerus_ are not very wide apart from each other. In both

there are five well-developed claws on feet and hands. They are British,

and generally Arctic and temperate in range. For some reason or other the

late Dr. Gray placed _Halichoerus_ in the same sub-family with the Walrus!

_Phoca_ is not only marine, but is found in the Caspian and in Lake Baikal.

Their existence in those inland seas is believed to be a vestige of a

former connexion with the sea. _Halichoerus grypus_ is a large seal 8 feet

in length when full grown. Its colour is yellowish grey, with darker grey

spots and blotches. It is not uncommon on the shores of our islands,

particularly of the Hebrides and Argyllshire. The commonest Seal is _Phoca

vitulina_, not more than 4 to 5 feet long, and of the same spotted

coloration as the last. This Seal has, however, a much wider distribution,

being Arctic as well as British, American, and North Pacific. A curious

fact about this Seal is that it is not impatient of fresh water; not only

will it ascend rivers, but it will live in inland lakes. It is said to be

especially sensitive to musical sounds. _P. hispida_ is British, but a rare

visitor to our islands. It is essentially an Arctic species. The Harp Seal,

_P. groenlandica_, is so called on account of a harp-shaped black bar in

the males, which starts at {453} the shoulders and extends to the thighs.

Like the other Seals mentioned, the young are white when first born. As may

be inferred from its scientific name this species is also Arctic in range.

It is also a rare visitor to these shores.

The genus _Cystophora_ is the only other genus of which there is a British

representative. It is called the Hooded Seal on account of an inflatable

sac upon the face, with which it is said to attempt to terrify its enemies.

The genus has an incisor less in each half of each jaw than _Phoca_ and

_Halichoerus_. Its formula is I 2/1 while these genera are both 3/2. _C.

cristata_ is a large species reaching a length of 10 feet. The colour of

the back is dark grey with deeper coloured spots. A few individuals only

have been recorded from our coasts.

_Stenorhynchus_ ( = _Ogmorhinus_) is an Antarctic genus. The hind-feet are

clawless. The incisors are 2/2. The molars have an additional cusp, _i.e._

three in all.

The genus _Leptonyx_ with but one species, _L. weddelli_, is purely

Antarctic in range. Like the last genus it has two incisors, and has but

rudimentary claws upon the hind-feet; the first and fifth toes moreover are

the longest. The genus chiefly differs from the last in the simple conical

crowns of the molars, which have not the additional cusps of

_Stenorhynchus_.

_Ommatophoca_ is another Antarctic genus with but a single species, _O.

rossi_. In this genus the hind-feet have no claws, and the first and fifth

toes are longer than the others. The claws of the fore-feet are

rudimentary. The immense size of the orbits gives the name to the genus.

There are two incisors, and the molars are all very small.

_Monachus_ is a northern genus inhabiting the Mediterranean and the

Atlantic in the vicinity of Madeira and the Canary Islands. It has

rudimentary nails upon both pairs of feet. The first and fifth toe of the

hind-feet are longer than the others. As with the preceding genera, the

incisors are two in each jaw. The species are _M. albiventer_, the

Monk-Seal, and _M. tropicalis_, the Jamaica Seal.

Allied to _Cystophora_ is the genus _Macrorhinus_, with (possibly) two

species, of which one is Antarctic, the other frequents or frequented the

coast of California. The incisors are two in the upper jaw, and but one in

the lower. The premolars are four and the molar one; all the teeth are

small and simple, but {454} have long roots. The nose of the male has a

dilatable proboscis. The southern Elephant Seal is _M. leoninus_, and

reaches a length of some 20 feet. It occurs on the shores of Kerguelen and

some other more or less remote islands. Its habits have been studied and

described by several observers, beginning with Anson in the last century.

The late Professor Moseley gave a good account of this marine monster in

his book on the voyage of the "Challenger." When the animal is enraged, the

end of the snout is dilated; but when this happens there is no long and

hanging proboscis such as has sometimes been described. The inflation

affects the skin on the top of the snout, which thus rises rather upwards

during inflation. The inflated region, according to Mr. Vallentin, quoted

by Mr. J. T. Cunningham, is about 1 foot long in an individual of 17 feet.

It has been stated that this proboscis is a temporary structure, only

appearing in the breeding season; but recent observations have shown that

this statement is inaccurate; it persists all the year round. The males

fight greatly during the breeding season, and produce a roar which has been

compared to the "noise made by a man when gargling." The females and the

young males bellow like a bull. The males fight of course with their teeth,

literally falling upon one another with their whole weight. Mr. Cunningham

thinks that the use of the proboscis is to protect the nose from injury; or

that it may be merely the result of "emotional excitement." In any case the

Bladder-nosed Seal, _Cystophora_, is undoubtedly protected from injury by

the possession of a corresponding hood. The nose is the most vulnerable

place, and the existence of this hood would stave off the effects of a blow

in that region. Moseley, however, has said of _Macrorhinus_ that it cannot

be stunned by blows on the nose as other Seals can; but he attributes this,

not to the dilated snout, but to the bony crest on the skull, and to the

strength of the bones about the nose. This Seal crawls with difficulty on

the land, and as the animals move "the vast body trembles like a great bag

of jelly, owing to the mass of blubber by which the whole animal is

invested, and which is as thick as it is in a whale."[324] When lying on

the shore, these animals scrape sand and throw it over themselves,

apparently to prevent themselves from being {455} incommoded by the direct

rays of the sun, to the effects of which they are very susceptible. The

Elephant Seal is mild and inoffensive, unless enraged, and, of course,

during the breeding season.

ORDER VIII. CREODONTA.

This entirely extinct group of Mammalia may be thus characterised:--Small

to large carnivorous mammals, with skull on the whole like that of the

Carnivora and with trenchant teeth; digits with unguiculate phalanges; tail

long; extremities usually with five, sometimes with four digits. In the

carpus a centrale is present, and the scaphoid and lunar are separate.

Interlocking of posterior dorsal and lumbar zygapophyses very perfect.

Brain small but convoluted.

This group, which corresponds with the CARNIVORA PRIMIGENIA of Mr.

Lydekker, is not easy to separate absolutely from the existing and more

especially from some of the extinct members of the CARNIVORA VERA. They

also come exceedingly near the Condylarthra, the presumed ancestors of the

Ungulata, and like them begin in the earliest Tertiary deposits. Their

likeness to the carnivorous Marsupials has also been insisted upon; but it

would seem that the succession of teeth in the Creodonta is typically

Eutherian.

The characteristics of the group may be exemplified by an account of the

genus _Hyaenodon_, after which some of the more important deviations in

structure shown by other genera will be referred to.

_Hyaenodon_ is both American and European, and ranges through the Eocene

and the Upper Miocene. It is a much-specialised Creodont, and therefore

exhibits well the distinctive characters of the group. About a dozen

species have been described. One of the best-known is the American _H.

cruentus_, and the following description refers to it. The back part of the

skull is low and broad, and is compared by Professor Scott (who has

described this and other species) as being "somewhat like that of an

opossum."[325] The whole skull is {456} long, and the top has a great

sagittal crest. The paroccipital processes are short and are closely

applied to the mastoid processes. The mesethmoid is larger than in the

carnivorous Marsupials, and the frontals are very large. The palate has a

peculiar structure; in most species the hinder ends of the palatines are

separated by a narrow fissure which broadens gradually, thus forming the

posterior nares. In _H. leptocephalus_ the posterior nares are brought very

far back by the meeting of the alisphenoids. The presphenoid, contrary to

what we find in the Dog, for example, is chiefly concealed by the vomer,

which covers it. The mandible has a long and strong symphysis, and its

angle is not inflected. The fore-limb is described as being "weak when

compared with the modern Carnivora." The scaphoid and lunar are separate,

and there is a centrale. The teeth present us with nearly the typical

formula. There is only one molar missing in the upper jaw. The canines are

enlarged. It has been suggested from a consideration of its palate that

_Hyaenodon_ was a semiaquatic animal; the deep cleaving at the extremities

of the phalanges seems to point in the same direction, since they resemble

in this the genus _Patriofelis_, which there are other reasons to regard as

aquatic. This latter genus has a fore-limb which is very like that of the

Pinnipedia, the digits are much spread out, and would seem to have

supported a kind of paddle. In any case it certainly fed upon aquatic

tortoises, for their remains have been found in its coprolites. The name

_Limnofelis_, also applied to what appear to have been members of this

genus, is suggestive of their habits. _Patriofelis_, at least one species,

seems to have been of about the size of a Lion.

_Mesonyx_ has a brain case which is actually smaller than that of the

Marsupial _Thylacinus_. The lachrymal bone is very large, and extends a

little way over the face, as is also the case with _Hyaenodon_; this

condition is also found in Insectivora and in _Thylacinus_. The axis

vertebra has a curiously-shaped spine, which is very different from the

hatchet-shaped process of that vertebra usual in the Carnivora, but is not

unlike what exists in the Arctoid genera _Meles_ and _Mydaus_. The limbs

show much disparity in length, and seem to argue a much-arched back when

the creature progressed. The carpus is stated to be strikingly like that of

the Insectivora. There is as in other Creodonts a separation between the

scaphoid and lunar; {457} the centrale appears to be present. The pelvis

"is most like that of the bear," the metacarpals and the tibia, and some

other bones, resemble those of the Hyaena. In fact this animal shows those

combined characters which are common in archaic forms.

* * * * *

{458}

CHAPTER XV

RODENTIA--TILLODONTIA

ORDER IX. RODENTIA[326]

Small to moderately large animals, furry, sometimes with spines. Toes with

nails of a claw-like character, or sometimes approaching hoofs. Usually

plantigrade, and only occasionally and partly carnivorous. Canine teeth

absent; incisors long and strong, growing from persistent pulps, and with

enamel only or chiefly on the anterior face, producing a chisel-shaped

edge; molars few (two to six), separated from the incisors by a wide

diastema. Caecum (nearly always present) very large, and often complicated

in structure. Brain, if not smooth, with few furrows, the hemispheres not

overlapping the cerebellum. Surface of skull rather flat; orbits not

separated from temporal fossae; malar bone in middle of zygomatic arch;

palate very narrow, with elongated incisive foramina; articular surface for

lower jaw antero-posteriorly elongated. Clavicles generally present. Testes

generally abdominal. Placenta deciduate, and discoidal in form.

The Rodents are a very large assemblage of usually small, sometimes quite

minute, creatures, embracing an enormous number of living generic types.

They are distributed all over the world, including the Australian region,

and, being small and often nocturnal, and by no means particular in their

diet, have managed to thrive and multiply to a greater extent than any

other group of living mammals. They are chiefly terrestrial creatures, and

often burrow or live in ready-made burrows. {459} Some, however, such as

the Voles, are aquatic; others, _e.g._ the Squirrels, are arboreal, and

there are "flying" Rodents exemplified by the genus _Anomalurus_. Their

range of habitat is in fact as wide as that of any other Order of mammals,

and wider than that of most.

[Illustration]

FIG. 231.--Side view of skull of Cape Jumping Hare (_Pedetes caffer_). x

3/5. _AS_, Alisphenoid; _Ex.O_, exoccipital; _Fr_, frontal; _L_, lachrymal;

_Ma_, malar; _Mx_, maxilla; _Na_, nasal; _OS_, orbito-sphenoid; _Pa_,

parietal; _Per_ points to the large supratympanic or mastoid bulla; _PMx_,

premaxilla; _Sq_, squamosal; _Ty_, tympanic. (From Flower's _Osteology_.)

The most distinct anatomical characteristic of the Rodents concerns the

teeth. They are without exception entirely deprived of canines. Thus there

is a long diastema between the incisors and the molars. Another peculiarity

is, that in many cases the dentition is absolutely monophyodont. In such

forms as the Muridae there seems to be no milk dentition at all. In that

family there are only three molars; but in other types where there are

four, five, or six molars, the first one, two, or three, as the case may

be, have milk predecessors, and may thus be termed premolars. This has been

definitely proved to be the case in the common Rabbit, which has the

unusually large number of six grinding teeth in each half of the upper jaw

when adult. The first three of these have milk forerunners. On the other

hand the existence of four molars does not apparently always argue that the

first is a premolar; for Sir W. Flower found that in _Hydrochoerus_,[327]

none of the teeth had any forerunners, at any rate so far as could be

detected from the examination of a very young animal. The Rabbit appears to

be also exceptional, in that the second incisor of the upper jaw and the

incisor of the lower jaw have milk forerunners. In any case the tendency

towards monophyodontism is peculiarly well-marked in this group of mammals.

The incisors of Rodents are as a rule in each jaw a single pair of long and

strong teeth, which grow from persistent pulps, and {460} grow to a very

great length, extending back within the jaw to near the hinder part of the

skull. These teeth are reinforced in the upper jaw by a small second pair

in the Lagomorpha only. The incisors are chisel-shaped, and often brown or

yellow upon the outer face, as is the case also with some Insectivores.

This peculiar shape, and their strength, renders them especially capable of

the gnawing action which characterises the Rodents. It has been pointed out

that where the incisors are wider than thick, the gnawing powers are feebly

developed; and that on the contrary, where these teeth are thicker than

wide, the animals are good gnawers. The incisors have often an anterior

groove, or it may be grooves.

[Illustration]

FIG. 232.--Molar teeth of Rodents. A, of Capybara (_Hydrochoerus_); B, of

Squirrel (_Sciurus_); C, of _Ctenodactylus_. (After Tullberg.)

The cheek teeth vary in number from two (_Hydromys_) to six (Rabbit) on

each side of the two jaws. Four is the prevailing number outside the large

division of the Rat-like Rodents. They are often set at an angle to the

horizontal plane of the jaw, looking outwards and obliquely to its

longitudinal axis; the individual teeth too are not unfrequently bowed in

form, reminding us of those of _Toxodon_. This of course only occurs in

those genera which have hypselodont teeth. The pattern of the teeth varies

much, and the different forms recall the teeth of more than one other group

of mammals. They are either bunodont or lophodont. In many cases the tooth

is encircled with a ridge of enamel, which is either almost simple or has a

more complicated contour; such teeth are by no means unsuggestive of the

Toxodonts. Some of the lophodont molars are by no means unlike those of the

Proboscidea. In _Sciurus vulgaris_ the {461} encircling ridge is broken up

into tubercles, which gives to the tooth a striking likeness to those of

_Ornithorhynchus_. Other genera have teeth like those of many Ungulates. It

has been shown by Sir J. Tomes[328] that the minute structure of the enamel

differs in different groups of Rodents.

The skull shows certain primitive characters. In the first place there is

no distinction between the orbital and the temporal fossa.[329] The sutures

between the bones retain their distinctness for very long. Other

characteristic features are the following:--The nasals are large, and so

are the paroccipital processes. The palate in front of the molars is not

distinct from the sides of the skull, its edge gradually becoming rounded

off above. It is also very narrow. The premaxillae are large in relation to

the great incisors. There is often a very much enlarged infra-orbital

foramen through which passes a part of the masseter muscle. The jugal bone

lies in the middle of the zygomatic arch, which is complete and enormously

enlarged in the Spotted Cavy (_Coelogenys paca_). As in many Marsupials,

the jugal bone sometimes extends backwards to the glenoid cavity, where the

lower jaw articulates. It is usually said with an absolute want of accuracy

that the cerebral hemispheres of the Rodents are smooth and without

convolutions. This error has been repeated again and again in text-books.

As a matter of fact the cerebral hemispheres of many forms are quite well

convoluted,[330] the degree of furrowing corresponding, as in so many

groups of mammals, with the size of the animal. This at any rate is

generally true, though the large Beaver with its scant convolutions is an

exception. The smaller forms, such as _Mus_, _Sciurus_, _Dipus_, and

_Cricetus_ are quite smooth-brained. The best furrowed brain of any Rodent

which has been examined is that of the huge _Hydrochoerus_. The Sylvian

fissure is very generally not pronounced; but is particularly well-marked

in _Lagostomus_. In all, or in most, Rodents the hemispheres are separated

by an interval from the cerebellum, the optic lobes being visible between

the two.

The mouth cavity of this group of mammals is divided into two chambers by a

hairy ingrowth behind the incisors; this arrangement is useful for animals

which use their strong incisors {462} as gnawing and excavating tools as

well as for the purposes of alimentation; for it allows of substances being

gnawed away without the products of the chisel-like action being taken into

the hinder cavity of the mouth. The Rodents have for the most part a simple

stomach of normal form; but in a few this is complicated by a marked

constriction, which divides the cardiac from the pyloric portions. The

Hamster, for example, is thus characterised. In all the members of the

order, with the exception of the Dormice and some allied forms, the caecum

is large and often sacculated. In some forms (e.g. _Arvicola_, _Myodes_,

_Cuniculus_) the large intestine is coiled upon itself in a spiral way--a

state of affairs strongly suggestive of Ruminants.

The Rodents are primarily divisible into two great groups, the

Simplicidentata and the Duplicidentata, characterised mainly by the upper

incisor teeth. In the former there is but one pair of these teeth; in the

latter a second smaller pair lie behind the former.

SUB-ORDER 1. SIMPLICIDENTATA.

SECTION 1. SCIUROMORPHA.

The Anomaluri are separated by Thomas and others from this section as an

equal section, while by Tullberg they are grouped with _Pedetes_.

FAM. 1. ANOMALURIDAE.--The genus _Anomalurus_ suggests at first sight the

Flying Squirrels of Asia, _Pteromys_. It is, however, an entirely African

genus, and is to be distinguished from the Asiatic Rodents by a series of

scales at the root of the tail, imbricated, keeled, and forming possibly a

"climbing organ." This character serves also to distinguish the present

genus from _Sciuropterus_. The cartilage, moreover, which supports the

patagium springs from the elbow. There are four molars in each half of each

jaw. The eyes and ears are large. There are five fingers and toes, but the

thumb is small, though provided with a nail. The sternum has seven joints,

and nine ribs reach it. The clavicle is strong. Huet, who has recently

monographed the genus,[331] allows six species. The species vary in size.

{463}

_Anomalurus peli_ appears, according to Mr. W. H. Adams,[332] to be a

common species on the Gold Coast; it is coloured black and white, but in

spite of the warning which this colour should convey, is considered by the

perhaps rather omnivorous native as "the greatest delicacy." The animal is

nocturnal, but affects only bright moonlight nights. Their "flying"

consists of a jump from a high branch to a lower one, after which they

reascend the tree to a point of vantage for another jump. They are said to

feed upon nuts; but Tullberg only found the remains of leaves in the

stomach.

_Idiurus_ is a lately-described genus allied to _Anomalurus_. There are at

any rate two species, _I. zenkeri_ and _I. macrotis_. The thumb is more

reduced than in _Anomalurus_, and the fibula, contrary to what is found in

that genus and in most Sciuromorphs, is fused with the tibia below.

A third genus, very recently described and allied to both the foregoing, is

_Aethurus_. It is a native of the French Congo,[333] and differs by the

absence of flying membranes. It has, however, the pad of large scales.

There is but one species, _A. glirinus_. It has a black bushy tail. The

postorbital processes of the frontals are totally wanting--there are not

even the traces to be seen in _Anomalurus_. The thumb has vanished. If we

are to compare _Anomalurus_ with the Squirrels then, thinks Mr. de Winton,

the present genus is probably diurnal by reason of the want of flying

membranes.

FAM. 2. SCIURIDAE.--The Squirrels, genus _Sciurus_, are world-wide in

range, the Australian region and the island of Madagascar being alone

excepted.

The eyes and the ears are large; the tail is of course long and bushy. The

fore-feet have an inconspicuous thumb; the hind-feet have four toes. The

soles of the fore-feet are naked or furry, those of the hind-feet are

hairy. There are twelve or thirteen dorsal vertebrae, and in correspondence

seven or six lumbars. The caudal vertebrae may be as many as twenty-five.

In the skull the frontals are broad, and there are long {464} postorbital

processes. The infra-orbital foramen is, as a rule, not large, but is

increased in size in a few forms. The number of separate pieces of bone in

the sternum is five. The molars of the upper jaw are five, but the first is

very small and soon drops out.

The Squirrels are often rather brilliantly coloured. The Chinese _Sc.

castaneiventris_ has grey fur with a rich chestnut-coloured under surface.

The Malabar Squirrel, _Sc. maximus_, as its name implies, a large animal,

has a deep reddish or chestnut-coloured fur above, which becomes yellow

below. The "Common Squirrel," "the lytill squerell full of besynesse,"

which is the Squirrel of this country, is brownish red on the upper parts

and white below. It ranges from this country as far east as Japan. Like

many other Rodents the Squirrel likes animal food and will eat both eggs

and young birds. "Camel's hair" brushes are made from this animal. The

genus _Tamias_, almost exclusively North American in range, is included by

Dr. Forsyth Major[334] in this genus, which then consists of considerably

over one hundred species.

The Ethiopian Ground Squirrels, genus _Xerus_, have a more elongated skull

than _Sciurus_, and the postorbital processes are shorter. The feet are not

hairy.

_Nannosciurus_ forms a perfectly distinct genus of Squirrels. These "Pygmy

Squirrels" differ in possessing a very elongated "face" and in the very

broad frontal region. The teeth are unlike those of _Sciurus_ in certain

features, and have been especially compared by Forsyth Major to those of

the Dormice. Four species of this genus are Malayan; one is West African.

The Bornean _Rheithrosciurus macrotis_ is the only species of its genus.

The genus may be distinguished by the exceedingly brachyodont molars, this

feature being more marked in this genus than in all other Squirrels. It is

called the "Groove-toothed Squirrel," from the "seven to ten minute

parallel vertical grooves running down the front face of its

incisors."[335]

The genus _Spermophilus_ includes a large number (forty or so) of

Palaearctic and Nearctic animals known as Sousliks. The ears are small;

there are cheek pouches as in _Tamias_. The general aspect of the animal is

like that of a Marmot, and they bridge over the exceedingly narrow gap

which separates the Marmots from the true Squirrels. Anatomically the skull

is like that of {465} _Arctomys_; the molars are five in the upper and four

in the lower jaw. The caecum is relatively speaking very small; the

measurements in a specimen of _S. tredecimlineatus_, dissected by Dr.

Tullberg, were: small intestine, 580 mm.; large intestine, 170 mm.; and

caecum, 27 mm. In _Tamias_ also the caecum is not greatly developed. These

animals are burrowing in habit.

The Prairie-dogs, genus _Cynomys_, of which the best-known species is

perhaps _C. ludovicianus_, are very like the Squirrels, but they are not

arboreal creatures; they live in burrows on the ground, as their vernacular

name denotes. The genus is entirely North American, and four species have

been differentiated.

The Prairie-dog or Prairie-marmot is some 10 inches to one foot in length.

The tail is no more than 2 inches. The ears are very small; the thumb is

fully developed and bears a claw. The measurements of the various sections

of the intestine are the following:--Small intestine, 860 mm.; large

intestine, 690 mm.; caecum, 75 mm. Thus the caecum is not large

comparatively speaking. These animals dig burrows on grassy plains which

they share with the Ground Owl (_Speotyto cunicularis_) and with

Rattlesnakes, all three species appearing to live in perfect amity.

Probably the Owls use the conveniently-constructed burrows, and the

Rattlesnakes come there to look after the young of both.

[Illustration]

FIG. 233.--Long-tailed Marmot. _Arctomys caudatus._ x 1/7.

Closely allied to the last are the Marmots, genus _Arctomys_. They differ

in the rudimentary character of the thumb and in the longer tail. The eyes

and ears are small. The distribution of the genus is Nearctic and

Palaearctic. There are ten species of {466} the genus. The Alpine Marmot,

_A. marmotta_, is familiar to most persons. The animal lives high up in the

Alps, and when danger threatens it gives vent to a shrill whistle. It

hibernates in the winter, and as many as ten to fifteen animals may be

found closely packed together in a single, carefully-lined burrow.

The only other European species is _A. bobac_, the Siberian Marmot, which

occurs in the extreme east of Europe, and is also Asiatic. There are four

North American species, including the Quebec Marmot, _A. monax_.

[Illustration]

FIG. 234.--Flying Squirrel. _Pteromys alborufus._ x 1/5.

The genus _Pteromys_ (of which the proper name, antedating _Pteromys_ by

five years, appears to be _Petaurista_) is confined to the Oriental region,

where there are a dozen species or so. The limbs are united by a parachute

extending to the toes, and supported anteriorly by a cartilage attached to

the wrists. There are also membranes anteriorly uniting the fore-limbs to

the neck, and posteriorly uniting the hind-limbs to the root of the tail

and a trifle beyond. The skull and the dental formula are as in Sciurus,

but the pattern of the molars, which is much complicated, seems to argue a

different mode of nutrition. There are twelve pairs of ribs. The large

intestine (in _P. petaurista_) is very nearly as long as the small, and the

caecum is also "colossal"; the measurements in an individual of the species

named were: small intestine, 670 mm.; caecum, 320 mm.; large intestine, 650

mm. {467} The caecum is disposed in a spiral. The teats are three pairs,

non-inguinal in position.

The size of these squirrels is 16 to 18 inches exclusive of the tail, which

is longer. These animals can make an exceedingly long jump with the help of

their flying membrane. Nearly eighty yards is the longest distance given

for these aerial excursions. It is stated that they are able to steer

themselves to some extent while in the air. As appears to be the case with

so many Rodents, these animals feed largely upon beetles and other insects,

besides bark, nuts, etc.

The allied genus _Sciuropterus_ has a much wider range. It extends into the

Palaearctic region and into North America, besides being found in India.

There is here no membrane reaching to the tail. The palms and soles are

furry. The caecum is very much shorter, and so is the large intestine. The

latter, in _S. volucella_, is not more than one-third of the length of the

small intestine. In other features there are no remarkable differences in

structure, save that the mammae, always three pairs, may be inguinal.

Of the genus _Eupetaurus_[336] but a single species is known, which is

limited to high altitudes at Gilgit and perhaps in Thibet. Its principal

difference from the other genera of Flying Squirrels is that the molars are

hypselodont instead of brachyodont. The interfemoral membrane is

rudimentary or wanting. The one species is _E. cinereus_. It is thought to

live "on rocks, perhaps among precipices." Dr. Tullberg attributes the

hypselodont teeth to the fact that the mosses upon which it is believed to

feed may have much sand and earth intermingled, which would naturally lead

to a more rapid wearing away of the teeth, and hence a need for a good

supply of dental tissue to meet this destruction.

FAM. 3. CASTORIDAE.--This, the third family of the Sciuromorpha, contains

but one genus, _Castor_, the Beaver, with at most two species, one North

American, the other European. This large Rodent has small eyes and ears, as

befits an aquatic animal, and the tail is exceedingly broad and covered

with scales; the transverse processes of the caudal vertebrae, in order

better to support the thick tissues lying outside them, are divided in the

middle of the series into two. The hind-feet are much larger than the

fore-feet, and are more webbed than in any other aquatic Rodent. {468}

In the skull the infraorbital foramen is small as in Squirrels. The

postorbital process has practically vanished. The four molars stand out

laterally from the jaws. The incisors, as might be surmised from the

habits, are particularly strong. The stomach has near the entrance of the

oesophagus a glandular patch, which seems to be like that of the Wombat

(see p. 144). In both sexes the cloaca is very distinct and comparatively

deep.

The two species of the genus are _C. canadensis_ and _C. fiber_. The latter

is of course the European species, which is now found in several of the

large rivers of Europe, such as the Danube and the Rhone. But it is

everywhere getting scarce, and limited to quite small and isolated

colonies.

In this country it is absolutely extinct and has been since before the

historic period. There is apparently no documentary evidence of its

survival down to this period. But the numerous names of places which are

called from this animal illustrate its former prevalence. Examples of such

names are Beverley in Yorkshire, and Barbourne or Beaverbourne in

Worcestershire. In Wales, however, Beavers seem to have persisted longer.

But they were rare in the Principality for a hundred years or so before the

Norman Conquest. The king Howel Dda, who died in 948 A.D., fixed the price

of a Beaver skin at 120 pence, the skins of Stag, Wolf, and Fox being worth

only 8 pence apiece. The Beaver was called by the Welsh "Llost-llyddan,"

which means "broad-tail." Its existence in the country is handed down in

the name of Llyn-ar-afange, which means Beaver lake. The last positive

record of the Beaver in Wales seems to be the statement of Giraldus

Cambrensis that in 1188 the animal was still to be found in the river Teivy

in Cardiganshire. In Scotland the Beaver is said to have continued down to

a later date. Ireland it never reached. The remains of this animal by their

abundance show the former prevalence of _C. fiber_ in this country. It is

known from the fens of Cambridgeshire, and from superficial deposits

elsewhere. The Thames formerly had its Beavers, and apparently it was

widely spread through the country generally.

The Beaver not only furnishes collars and cuffs for coats; it was used, as

every one knows, to provide hats. But the usefulness of the animal by no

means ended here in the eyes of our {469} forefathers. The Rev. Edward

Topsell observed that "for giving great ease unto the gowt the skinnes of

beavers burned with drie oynions" are excellent. Castorein as a drug, if

not in actual use, has quite recently been a part of the pharmacopoeia. It

is derived from the anal glands common to this and other Rodents, and

indeed many other mammals.

A large extinct form of Beaver is _Trogontherium_,[337] found in the

"Forest-bed" of Cromer. The skull is about one-fourth longer than that of

_Castor_. It has a less inflated bulla, and slightly more pronounced

postorbital processes than _Castor_. The third molar (fourth grinding

tooth) is relatively larger than in _Castor_, and has a rather more folded

crown. The foramen magnum is more triangular.

FAM. 4. HAPLODONTIDAE.--A separate family seems to be required for the

genus _Haplodon_, whose characters will therefore be merged with those of

its family. It is to be distinguished from most other Squirrel-like

creatures by the fact that there is no postorbital process to the frontal.

The molar teeth are five in the upper and four in the lower jaw. The

Sewellel, _H. rufus_, like the other species of the genus (_H. major_), is

found in North America west of the Rocky Mountains. It has the habit of the

Prairie-marmot, and has a short tail, only moderately long ears, and

five-toed feet. Tullberg is of opinion that this animal nearly represents

the ancestral form of the Squirrel tribe.

SECTION 2. MYOMORPHA.

This subdivision of the Rodents contains, according to Mr. Thomas's recent

estimate,[338] no less than 102 genera. It is therefore obviously

impossible to do more than refer to some of the more interesting of these.

This group is again divided into the following families:--

(1) Gliridae, including the Dormice.

(2) Muridae, the Rats, Mice, Gerbilles, Australian Water-rats, Hamster.

(3) Bathyergidae, Cape Mole, etc.

(4) Spalacidae, Bamboo Rats. {470}

(5) Geomyidae, Pouched Rats.

(6) Heteromyidae, Kangaroo Rats.

(7) Dipodidae, Jerboas.

(8) Pedetidae.

The Gliridae have no caecum, so usual in the Rodentia. It is true that all

the genera have not been dissected, but it is known that in the true

Dormice, as well as in the genus _Platacanthomys_, a caecum is absent.

Apart from these few exceptions the Mouse-like Rodents all possess a

caecum, though it is often not very large. They are all smallish animals,

and are modified to a great variety of habit and habitat. There are

burrowing, swimming, and climbing forms. The group is universal in range,

even including the Australian region, in which they are the only Rodents.

FAM. 1. GLIRIDAE.--This family, also called Myoxidae,[339] includes the

Dormice, and is entirely an Old-World family, absent only from the Malagasy

region. Its most important differential character is the total absence of

the caecum and of any sharp boundary between the small and large intestine.

The molars are usually four. The eyes and ears are well developed.

The genus _Muscardinus_ includes only the Common Dormouse, _M.

arellanarius_. This small creature, 3 inches long with a tail of 2-1/2

inches, is, of course, a well-known inhabitant of this country. It is also

found all over Europe. It is not particularly abundant in this country, and

a good specimen is said to be worth half a guinea. As the specific name

denotes, it lives largely on hazel nuts; but it will also suck eggs and

devour insects. The animal makes a "nest" in the form of a hollow ball. Its

hibernation is well known, and has also given rise to the German name

("Schlaefer") of the group. It was well known to Aristotle, who gave or

adopted the name [Greek: Eleios] for the animal. Its winter

sleep--suggestive of death--and its revivification in the spring gave the

Bishop of Salamis, Epiphanius, an argument for the resurrection of man. The

fur was reckoned in Pliny's time a remedy for paralysis and also for

disease of the ears.

The genus _Myoxus_ includes also but a single species, _M. glis_, the

so-called "Fat Dormouse" of the Continent. It has no {471} glandular

swelling at the base of the oesophagus, such as occurs in the last genus

and in _Graphiurus_. Of _Graphiurus_ there are thirteen species, all

African in range. The genus does not differ widely from the last. There is,

however, a glandular region of the oesophagus. _Eliomys_ is the last genus

of typical Dormice. It is Palaearctic in range.

_Platacanthomys_, of a Dormouse-like form, has like other Dormice a long

tail, on which the long coarse hairs are arranged in two rows on opposite

sides towards the tip; it is represented by a single species, _P.

lasiurus_, from the Malabar coast. It is arboreal in habit. The fur is

mingled with flattened spines. The molars are reduced to three on each side

of each jaw. This form has been bandied about between the "Mice" and the

"Dormice"; but Mr. Thomas's discovery of the absence of the caecum argues

strongly in favour of its correct location among the Gliridae. _Typhlomys_

is an allied genus, also from the Oriental region. This and the last are

placed in a special sub-family of the Gliridae, Platacanthomyinae, by Mr.

Thomas.

FAM. 2. MURIDAE.--This family, that of the Rats and Mice in a wide sense,

is the most extensive family of Rodents. In it Mr. Thomas includes no less

than seventy-six genera. The molars are generally three. The tail is fairly

long, or very long, and the soles of the feet are naked.

SUB-FAM. 1. MURINAE.--The true Rats and Mice may be considered to form a

sub-family, Murinae. The genus _Mus_, including the Rats and Mice in the

limited sense of the word, contains about 130 species. They are exclusively

Old World in range, being only absent from the Island of Madagascar. In the

New World there are no species of the restricted genus _Mus_. The eyes and

the ears are large; the pollex is rudimentary, and bears a nail instead of

a claw. The tail is largely scaly. All the members of the genus are small

animals, some quite minute. In this country there are five species[340] of

the genus, viz. the Harvest Mouse, _M. minutus_, which has a body only

2-1/2 inches long with an equally long tail. It is the smallest of British

quadrupeds with the exception of the Lesser Shrew. The Wood Mouse, _M.

sylvaticus_, is about twice the size; it differs also from the last species

in that it {472} frequents barns, and is thus sometimes mistaken for the

Common Mouse, from which, however, it is to be distinguished by its

coloration and longer ears. The latter, _M. musculus_, is too familiar to

need much description. A curious variety of it has occurred. This has a

thickened and a folded skin like that of a Rhinoceros, and the hair has

disappeared. The Black Rat, _M. rattus_, is like a large Mouse, and is

smaller and blacker in colour than the "Hanoverian Rat." It is sometimes

called the "Old English Rat," but seems nevertheless to be not a truly

indigenous Rodent. It has been so defeated by competition with the

Hanoverian Rat that it is now not a common species in this country.

The Hanoverian or Brown Rat, _M. decumanus_, is a larger and a browner

animal than the last. It is very widely distributed through the globe, no

doubt largely on account of the fact that it is readily transported by man.

The same is the case with the Common Mouse, whose real origin must be a

matter of doubt. The original home of the Brown Eat is thought by Dr.

Blanford to be Mongolia. There is so far a justification for the name

"Hanoverian Rat" that the animal seems to have reached this country about

the year 1728. But there is no reason for calling it, as is sometimes done,

the Norway Rat.

Some members of this genus, whose fur is interspersed with spines, or which

are quite spiny, have been separated as a genus, _Leggada_, which, however,

is not generally allowed.

Closely allied again is _Chiruromys_, which has a strongly prehensile tail,

a feature which is not common among the Myomorpha, though _Dendromys_, a

tree-frequenting form, and _Mus minutus_, already spoken of, show the same

character. Many Mice seem to have prehensile tails, which they can curl

round branches; but it is not so fully developed as in the species just

named.

A number of other genera are referable to the true Mice, the sub-family

Murinae of Thomas's classification. The Syrian and African _Acomys_ has

very spiny fur, so much so that "when it has its spines erected it is

almost indistinguishable at the first glance from a diminutive hedgehog."

The genera _Cricetomys_, _Malacomys_, _Lophuromys_, _Saccostomus_,

_Dasymys_ are restricted to the Ethiopian region. _Nesokia_ is Oriental,

reaching {473} also the Palaearctic region. _Vandeleuria_, _Chiropodomys_,

_Batomys_, _Carpomys_ are Oriental, the last two being confined to the

Philippines.

Another peculiar Philippine genus is _Phlaeomys_, of large size, and allied

to it is _Crateromys_, originally confounded with it. _Batomys granti_ is

also confined to Luzon. Its molars are three, like those of the also

restricted and Philippine _Carpomys melanurus_, which is an arboreal form.

There is a second species, _C. phaeurus_.

_Phlaeomys_ is placed, however, by Mr. Thomas in a distinct sub-family of

its own, PHLAEOMYINAE, and is removed from the Murinae.

_Hapalomys_, with but one species, is Burmese. _Pithecochirus_ is Javanese

and Sumatran. _Conilurus_ (also known as _Hapalotis_) is a genus containing

species which are termed Jerboa Rats, on account of their mode of

progression. They are desert and Australian forms. There are sixteen

species.

[Illustration]

FIG. 235.--Spiny Mouse. _Acomys cahirinus._ x 1/2.

_Mastacomys_, with one species, is limited to Tasmania. _Uromys_, with some

eight species, is from Queensland, and inhabits also the Aru Islands and

the Solomon Islands. The Celebesian _Echiothrix_, or _Craurothrix_ as it

should apparently properly be called, is another genus containing but a

single species. _Golunda_ is both Oriental and Ethiopian, one species

occurring in each region. The beautiful little striped Barbary Mice,

_Arviacanthis_ (or _Isomys_), are African, north as well as tropical.

The genus _Saccostomus_ resembles the Hamsters in the presence of cheek

pouches. Its teeth, however, are Murine. It agrees with _Steatomys_ in the

comparatively short tail. The caecum is rather long. {474}

SUB-FAM. 2. HYDROMYINAE.--The genus _Hydromys_,[341] of which there are

several species, the best known being _H. chrysogaster_, is an exclusively

Australian form, and is aquatic in habit. It is a foot or so in length, and

has a fairly long tail. The fore- and hind-limbs are webbed, in

correspondence with its habits. The Australian Water-Rat is black, with an

admixture of golden-coloured hairs dorsally and golden colour below, with a

lighter median stripe. The thumb is small, and the webbing of the hands is

not so marked as is that of the feet. The molars are only two in each half

of each jaw. The caecum is rather small, the measurements of the alimentary

canal being: small intestine, 895 mm.; large intestine, 278 mm.; caecum, 70

mm. Allied to the last is _Xeromys_, a genus which is also Australian, but

limited to Queensland. It has been established by Mr. Thomas,[342] who

discovered that it has the same reduced formula as _Hydromys_. _Xeromys_,

however, is not an aquatic animal, and has unwebbed feet.

In the Luzon highlands Mr. Whitehead has discovered, and Mr. Thomas quite

recently described,[343] a number of peculiar Rodents. Of these the genera

_Chrotomys_, _Celaenomys_, and _Crunomys_ are allied to the Australian and

New Guinea _Hydromys_.

_Chrotomys whiteheadi_ is unusual among Muridae, in its coloration being

marked by a pale stripe down the back. The creature is the size of the

Black Rat (_Mus rattus_). It is terrestrial not aquatic in habit, in spite

of its likeness to _Hydromys_. The molars, however, are 3/3.

_Crunomys fallax_ is more like _Hydromys_. It has, however, three molars,

as in the last genus. But the skull has the flattened form characteristic

of _Hydromys_ as opposed to _Mus_.

Like _Batomys_, _Celaenomys silaceus_ is also somewhat intermediate between

_Hydromys_ and _Mus_. It is described as very Shrew-like in appearance, and

has a very pointed muzzle. Its habits Mr. Whitehead is "quite unable even

to guess at." Like _Hydromys_ and _Xeromys_ this Rodent has but two molars.

SUB-FAM. 3. RHYNCHOMYINAE.--The genus _Rhynchomys_, containing but one

species, _Rh. soricioides_ (of Thomas), is also, as both its generic and

specific names imply, a somewhat Shrew-like form in external aspect. The

skull, too, is Insectivore-like in its {475} elongation, and the lower

incisors are worn to needle-like points. The two molars are excessively

minute, and thus the always large gap in the jaws is greatly exaggerated.

It is suggested that this Rat is an insect-eater, but nothing positive is

known.

SUB-FAM. 4. GERBILLINAE.--The Gerbilles form another sub-family,

Gerbillinae, of the Muridae, or a family, according to some. The best-known

genus is _Gerbillus_, including the Gerbilles proper. These animals are Old

World in range, belonging to the three regions of that part of the world.

There are a large number of species in the genus, over thirty. They have a

Jerboa-like form, with rather long hind-limbs and a long and hairy tail.

But the hind- as well as the fore-feet are five-toed. The molar teeth have

no trace of tubercles, but only transverse lamellae of enamel. The incisors

are orange; they are white in _Dipus_. _Gerbillus pyramidum_ is 90 mm.

long, with a tail of 125 mm. The ears are long, 13 mm. The tail has longer

hairs at the tip.

[Illustration]

FIG. 236.--Gerbille. _Gerbillus aegyptius._ x 1/2.

_Psammomys_ is in some respects different. The tail is shorter than in

_Gerbillus_; its length in an individual of 165 mm. was 130 mm. As in

_Gerbillus_ there are four pairs of teats, two pectoral and two inguinal.

This genus is exclusively Palaearctic in range. _Meriones_ has a range

co-extensive with that of _Gerbillus_.

_Pachyuromys_ is an Ethiopian genus with a short tail. As the generic name

denotes, the tail is not only short but thick and fleshy.

SUB-FAM. 5. OTOMYINAE.--The allied genera, _Otomys_ and _Oreinomys_, are

Ethiopian. _Otomys unisulcatus_ has a tail shorter than the body, the

measurements of a female of this species being 137 mm. with a tail of 87

mm. The ear is long, whence the name; it measured in this specimen 20 mm.

{476}

SUB-FAM. 6. DENDROMYINAE.--The genus _Deomys_ is an African form,

consisting of only one species from the Congo region. _D. ferrugineus_ has

a reddish colour as its name implies; the soles are quite naked and the

tail is long and slender. It is considerably longer than the body,

measuring (minus a fragment of the tip) 172 mm., while the body is 125 mm.

long. The characters of the molar teeth, which are three, are intermediate

in their form between those of the true Rats and those of the Hamsters.

_Dendromys_ is also Ethiopian in range. There are several species. _D.

mesomelas_ is a smallish creature, 60 mm. long, with a tail of 90 mm.

_Steatomys_ is another African genus, allied to the last. Its tail,

however, is only half the length of the body. The two remaining genera are

_Malacothrix_ and _Limacomys_. Their range is African.

SUB-FAM. 7. LOPHIOMYINAE.--Allied to the Hamsters is the singular East

African genus _Lophiomys_, with only one species, _L. imhausi_, of

Milne-Edwards.[344] The size is between that of a Rabbit and of a

Guinea-pig. The stomach is curved and somewhat intestiniform. It has been

termed the Crested Rat on account of the "prominent crest of stiff hair

running down the back." The fingers and toes are five, and the very long

tail is clad with hair longer than that upon the body generally. The pollex

is rudimentary, and the hallux is opposable.

The most remarkable structural feature in this genus concerns the skull,

and on account of this it has been regarded as the type of a separate

family. The temporal fossa behind the eye is covered over by a complete

bony plate, formed by a downgrowth of the parietal, meeting an upgrowth

from the malar; this singular arrangement of the bones recalls the

conditions which obtain in turtles. The whole skull, moreover, is covered

with symmetrically disposed granulations, such as are found in no other

mammal; it suggests rather the skull of certain fish. It is believed that

the bony plate already referred to is not really a portion of the bones of

which it appears to be a prolongation, but merely an ossification of

fasciae in this region. The atlas is granulated like the skull; there are

sixteen pairs of ribs and a feeble clavicle. The molars are three, and of a

peculiar form. {477} They have, in the case of the first three, transverse

ridges, from which stand up two sharp and long tubercles. The other teeth

have two ridges. The incisors are pale yellow. The shape of the teeth and

the smallness of the caecum suggest that this Rodent is not so purely a

vegetarian as others, and that it nourishes itself largely upon insects.

SUB-FAM. 8. MICROTINAE.--The Voles or Water-Rats form a distinct group of

Murine animals, to which the sub-family name of Microtinae has been applied

from the genus _Microtus_ (more generally known as _Arvicola_), a genus

which includes the Water-Rat and Field-Voles of this country. This genus

has short ears, and a short and hairy tail. Its build is stouter and

clumsier than that of the Rats. The genus is confined to the Palaearctic

and the Nearctic regions. In this country there are three species. The best

known is the Water-Vole or Water-Rat, _M. amphibius_, which has been seen

by most people, and which frequents streams, ponds, and canals. The feet,

curiously enough, are not webbed, which seems to argue the recent adoption

of an aquatic life. Mr. Trevor-Battye has remarked that this animal, when

swimming at leisure, uses its hind-limbs only, carrying the fore pair at

the sides like a Seal. The Bank-Vole, _M. glareolus_, is rather a local

species in this country. It is a terrestrial Vole, and burrows. The

Field-Vole, _M. agrestis_, has become notorious on account of the

"plagues," to which its immense numbers have on occasions given rise. It is

the smallest species, and has a greyish-brown fur like the Water-Vole, the

Bank-Vole being redder. To give an idea of the cost of the depredations of

this animal, Mr. Scherren quotes[345] a farmer who gave evidence before the

Agricultural Commission to the effect that, putting the damage of one Vole

at two pence, the amount of loss suffered on a farm of 6500 acres in two

years would be L50,000!

The genus _Fiber_ comes very near the last. It is a North American genus.

The hind-feet are slightly webbed; the tail is a trifle shorter than the

body, and is compressed and scaly, with scattered hairs. The thumb is

short, but with a fully-developed claw. As in the last genus, the small and

large intestines are roughly of the same length, and the caecum is about

one-fourth of the length of either. It is known as the "Musquash." {478}

Of _Fiber zibethicus_, or rather a closely-allied form, _F. osoyoosensis_,

from Lake Osoyoos near the Rockies, Mr. Lord writes[346] that it constructs

for itself a house of bulrushes built up from the bottom in 3 or 4 feet of

water. It is dome-shaped, and rises about a foot out of the water. "If a

dead or badly-wounded duck be left on the pool, it is at once seized on,

towed into the house, and doomed." Thus it appears that this Rodent, like

so many others, is largely carnivorous. It has also been asserted that it

eats fish.

_Neofiber_ is an allied genus, North American in range. The species, _N.

alleni_, is compared, as regards outward form, with the Water-Vole, _M.

amphibius_. It has, however, a shorter tail.

Another very well-known member of this sub-family is the Lemming. The name,

however, applies to two quite distinct genera. The genus _Cuniculus_,

including the Banded Lemming, _C. torquatus_, is an inhabitant of North

America, Siberia, and Greenland. The tail is short, its length being 12 mm.

as against a body length of 101 mm. The feet are furred beneath, a not

unusual state of affairs in Arctic mammals. The ears are very slight. The

thumb is well developed, and bears a claw.

In _Myodes_, on the other hand, which is not so markedly an Arctic animal,

though occurring in both Palaearctic and Nearctic regions, the ears are

rather bigger, though still smaller than those of _Microtus_. The under

surfaces of the feet are similarly furred. The tail is also short. It is

commonly said that the two genera are to be distinguished by the furred

feet of _Cuniculus_, and by the absence of fur in the present genus. That,

according to Tullberg, does not appear to be the case. The differences are

thus so much reduced that it seems almost unnecessary to retain the two

genera. The best known species of _Myodes_ is of course the Scandinavian

Lemming, _M. lemmus_. This animal used to occur in this country in

Pleistocene times (as did also _C. torquatus_), and recently Dr. Gadow has

found remains with skins attached in caves in Portugal. It may still

survive in the mountains of the Peninsula.

The actual habitat of the Lemming in Scandinavia is the great tablelands,

3000 feet high in the centre. The migrations do not take place with

regularity; even twenty years may elapse before the appearance in

cultivated lands of those countless {479} hordes so familiar (as far as

their description is concerned) to everybody. The Lemmings do not return

from their exodus. They die from various causes, including combats with one

another. Their chief foes, however, are Wolves and Gluttons, Buzzards and

Ravens, Owls and Skuas, which batten on the migrant hordes. Their sudden

increase in numbers recalls the similar increase at times of the

Field-Vole, to which reference has already been made.

_Ellobius_ is an Old-World genus, which leads a "Talpine" life, and has in

consequence rudimentary external ears and very small eyes. The tail is

short. Contrary to what might be expected from its mode of life, the claws

upon the digits are not strong.

The remaining genera of Vole-like Murines are _Phenacomys_ and _Synaptomys_

from North America, and Siphneus from Palaearctic Asia. _Evotomys_ is one

of those genera which are common to both the Palaearctic and the Nearctic

regions, but the bulk of the species are North American.

SUB-FAM. 9. SIGMODONTINAE.--This is the name given to another sub-family of

Murine Rodents, a group which includes the Hamsters in the Old World as

well as a large number of South American genera of Rat-like animals. Of

these latter there are a very large number, the bulk of the group being

American.

The Hamsters, genus _Cricetus_, as it is usually called, although

apparently the correct name is Hamster, are Old-World forms of Pouched

Rats. The Common Hamster, _C. frumentarius_, is about 210 mm. long, with a

tail of 58 mm. It has cheek pouches. The small and the large intestines are

not very unequal in length, and the caecum is fairly large, being about

one-sixth to one-seventh of the length of either. It is a purely

vegetable-feeding creature, and in Germany where it occurs (and from which

language its vernacular name is derived), hibernates during the winter in

its burrow, having previously surrounded itself with a great accumulation

of food carried thither.

To North America are peculiar the genera _Onychomys_, _Sigmodon_, and

_Peromyscus_. The genus _Sigmodon_, the Cotton Rats, reaches Central

America, and even gets a little farther south. The other two genera, though

mainly North American, also extend their range to the south. _Onychomys_

has hairy {480} foot-pads, a state of affairs which characterises a number

of these Rodents.

The genera _Megalomys_, _Chilomys_, _Reithrodontomys_, _Eligmodontia_,

_Nectomys_, _Rhipidomys_, _Tylomys_, _Holochilus_, _Reithrodon_,

_Phyllotis_, _Scapteromys_, _Acodon_, _Oxymycterus_, _Ichthyomys_,

_Blarinomys_, _Notiomys_ are South American forms. _Oryzomys_ and

_Rheithrodontomys_ are common to both parts of the New World.

The genus _Ichthyomys_ is remarkable on account of its un-Rodent-like

habits and of certain associated structural changes. _I. stolzmanni_ was

obtained from Mount Chanchamays in Peru at an altitude of 3000 feet; it is

a habitual fish-eater, and lives in streams. Another species, _I.

hydrobates_, was formerly referred to _Habrothrix_. The skull shows

likenesses to that of the Australian _Hydromys_; but the most marked

characters of adaptation are those of the teeth and caecum. The cutting

edges of the upper incisors form a reversed [347] of obvious use in holding

a slippery fish. The caecum is much reduced, short, and narrow. The general

Otter-like shape of the creature is largely due to its flattened head,

though its "size and general proportions are much as in the common Black

Rat."[348]

This sub-family contains a number of genera from Madagascar, viz.

_Brachytarsomys_, _Nesomys_, _Hallomys_, _Brachyuromys_, _Hypogeomys_,

_Gymnuromys_, and _Eliurus_.

SUB-FAM. 10. NEOTOMINAE.--The last sub-family of the Muridae is that of the

Neotominae, containing the North American genera _Neotoma_, _Xenomys_,

_Hodomys_, and _Nelsonia_.

FAM. 3. BATHYERGIDAE.--This family contains several genera which consist of

subterranean forms. All these Rodents agree in a number of characters, of

which the principal are as follows:--

The eyes are very small, and the external ears are reduced to the merest

fringe of skin round the aural aperture. The legs are short, as is the

tail; the hair-covering is reduced--a reduction which finds its culmination

in the nearly nude _Heterocephalus_. Being burrowing creatures, a number of

other modifications in accordance with this mode of life are to be seen in

their structure. The upper incisors stand out in front of the closed lips,

and prevent the entrance of earth. For the same reason {481} the nostrils

are small, and the forehead but little expanded between them.

The genus _Bathyergus_ contains but a single species, the Cape Mole-Rat,

which is found in Southern Africa; it is of moderate size, not exceeding a

small Rabbit in dimensions. On the fore-limbs are exceedingly long claws,

of which that borne by the second finger is the longest, and the claw of

the thumb the shortest. The hind-feet have by no means such long claws. The

scratching and burrowing is naturally chiefly effected by the fore-limbs.

The small and large intestines are of equal length, and each is rather more

than six times the length of the caecum; in these measurements the present

genus differs from the next.

_Georhychus._--Of this African genus there are about ten species. The claws

are not so long as in the last genus, but there are, as in _Bathyergus_,

four molar teeth on each half of each jaw. The intestinal measurements in

an example of _G. capensis_ were: small intestine, 25 inches; caecum, 4

inches; large intestine, 15 inches.

The genus _Myoscalops_ or _Heliphohius_ (also with an African range) has

six back teeth on each side. A number of species sometimes referred to the

last genus are placed here by Mr. Thomas. The claws are small.

One of the most remarkable genera of this family is the little

_Heterocephalus_ from Abyssinia and Somaliland. As Mr. Thomas justly

remarks,[349] it "is a peculiar-looking little creature, about the size of

the Common Mouse, but looking almost more like a tiny hairless puppy on

account of its nearly naked skin, small eyes, and peculiar physiognomy."

Though apparently naked, there are numerous scattered hairs over the entire

body, and the toes are fringed with stiffish hairs, which must be

advantageous to a burrowing animal. There are two species, _H. glaber_

(originally described by Rueppell), and _H. phillipsii_, of which our

knowledge is due to Mr. Thomas. The length of the entire creature including

the tail is not more than 134 mm., both species being approximately of the

same dimensions. Mr. Lort Phillips, the discoverer of the species which

bears his name, writes "that this little creature, called 'Farumfer' by the

Somali, throws up in places groups of miniature craters, which exactly

resemble volcanoes in active eruption. When the little beasts were at {482}

work, I used frequently to watch them, and found that the loose earth from

their excavations was brought to the bottom of the crater, and sent with

great force into the air in a succession of rapid jerks, and that they

themselves never ventured forth from the shelter of the burrows."[350]

FAM. 4. SPALACIDAE.--"The Spalacidae," observes Dr. Blanford, "are

sometimes called rodent moles, and resemble a mole in general aspect,

having cylindrical bodies, short limbs, small eyes and ears, large claws,

and a short or rudimentary tail." The existence of a spiral valve in the

caecum may perhaps characterise this family; but it has at present only

been found in the two genera _Spalax_ and _Rhizomys_.

_Spalax_ has inconspicuous eyes and external ears. The tail is totally

absent. The lower incisors are more developed than in other Rodents; they

project in a bony sheath beyond the posterior end of the ramus of the lower

jaw. The scapula is long and narrow. The large intestine is half the length

of the small intestine. The animal seems to have only two pairs of teats,

one pectoral the other inguinal.

_Spalax typhlus_ of Egypt, which is probably not different from the

European form, makes extensive burrows, some of the branches being even 30

to 40 yards in length. In a "domical chamber," situated along the course of

one of these burrows, Dr. Anderson found no less than 68 bulbs stored up.

Its eyes are mere black specks among the muscles, but they appear, however,

to have a proper organisation. There are altogether eight species of the

genus, which is entirely Palaearctic in its range.

The genus _Rhizomys_, including a number of species known as Bamboo Rats,

is purely Oriental in range. _Rh. sumatrensis_ reaches a length of 19

inches; the better-known species, _Rh. badius_, is at most only 9 inches in

length--in both cases the measurements are exclusive of the tail, which is

a quarter to one-third of the length of the body, and is not scaly but

nearly naked, with a few scattered hairs. The molars are three, and the

incisors usually orange in colour; but sometimes the upper incisors are

white as in _Rh. badius_. There are thirteen dorsal vertebrae. In _Rh.

pruinosus_ the large intestine is considerably longer than the small

intestine; the lengths of the two sections of the gut are 42 and 30 inches

respectively. In another {483} species the large intestine is slightly

shorter than the small intestine. In _Rh. badius_ the two parts of the gut

are almost exactly equal in length. There are three pairs of inguinal and

two pairs of pectoral teats. The name _Rhizomys_ appears to have been given

to the animals of this genus for the reason that they feed largely on

roots. They burrow, and, like many other burrowing animals, feed in the

evening. As is the case with other forms, _Rhizomys_ is said to burrow with

the assistance of its teeth as well as of its claws.

[Illustration]

FIG. 237.--Bamboo Rat. _Rhizomys badius._ x 1/4.

_Tachyoryctes_ is an African genus closely allied to the last. There are

three Ethiopian species. It is mainly to be distinguished by the different

pattern upon the grinding surface of the molars.

FAM. 5. GEOMYIDAE.--This family of burrowing Rodents is limited to North

and Central America. The animals have cheek pouches, and small eyes and

ears, in accordance with their mode of life. The claws of the fore-limbs

are very strongly developed.

The genus _Geomys_ contains some eight species, which are Central and North

American, not extending, however, far north. The incisors of the upper jaw

are grooved with two grooves. There are three pairs of teats--one axillary,

and the two remaining inguinal.

_Thomomys_, without grooves on the incisors, reaches to Canada in the

north, and does not extend as far south as the last genus. {484}

Allied to this family, and indeed united with it by Tullberg, but kept

separate by Thomas, is the

FAM. 6. HETEROMYIDAE.--The members of this family are also American, but

are not confined to the northern-central regions of that continent, for the

genus _Heteromys_ extends into South America.

The genus _Dipodomys_, with twelve species, is of a Jerboa-like form, as

the following measurements of an example of _D. merriami_ will show. The

length of the head and body was 85 mm.; of the tail 127 mm.; the hind-foot

is 32 mm. It has but four toes. The hind-limb is longer than the

front-limbs.

In _Perodipus_ the same form is exhibited. There are, however, five toes,

and the sole of the foot is hairy. The axis vertebra and the two following

vertebrae are fused together.

_Perognathus_ is a third genus. It has the same general slender form, but

the tail is not so long, being but little longer than the body. The

hind-limbs, too, are shorter. The teats of this and of _Perodipus_ are as

in _Geomys_. The two remaining genera of the family are _Heteromys_ and

_Microdipodops_.

[Illustration]

FIG. 238.--Jerboa. _Dipus hirtipes._ x 1/3. Eastern Europe.

FAM. 7. DIPODIDAE.--This family consists of small, plain-living, and

leaping or arboreal creatures, commonly known as Jerboas. The main

anatomical characters of the family are the following:--There is a large

infra-orbital foramen. The molars are always reduced, the premolar being

either absent in the lower jaw alone or in both jaws. This family presents

an obvious likeness to _Dipodomys_ (hence the name of the latter) and to

some other members of the American family Heteromyidae {485} There is even

the same ankylosis of the neck vertebrae. We find, moreover, the same

association of long-legged and shorter-legged forms that characterises the

Heteromyidae.

[Illustration]

FIG. 239.--Bones of right pes of Jerboa, _Dipus aegyptius_. x 3/4. _a_,

Astragalus; _c_, calcaneum; _c_^2, middle cuneiform; _c_^3, outer

cuneiform; _cb_, cuboid; _n_, navicular; I-IV, first to fourth toes. (From

Flower's _Osteology_.)

The typical genus _Dipus_ is a smallish quadruped with long naked ears and

a long tail. The ten species are all Palaearctic in range. The fore-limbs

are short and five fingered, and the short pollex has no claw; the

hind-limbs are excessively long and only three-toed. The bony structure of

these limbs is remarkable. The three metatarsals are elongated almost like

those of a bird, and are ankylosed together. The digits have long phalanges

which alone reach the ground as the animal hops. It is a curious fact, and

one not so easily identifiable with the way of life, that the neck

vertebrae of this genus are ankylosed together with the exception of the

atlas, which is free; the arrangement is precisely like that of the Sperm

Whale. The last vertebra is, however, sometimes free. The Jerboas not only

leap but they burrow, and their strong incisors are said to be used in

burrowing through stony ground. They are eaten by the Arabs, and are, or

have been, called Daman Israel, _i.e._ Lamb of Israel. In _D. hirtipes_ the

body and tail measure respectively 4-1/2 and 7 inches. The hind-feet have a

tuft of long hairs below. Mr. W. L. Sclater's newly-founded genus

_Euchoreutes_[351] is somewhat more primitive in its characters than is

_Dipus_. The general form is the same, with long ears and a long tail. But

there are five toes to the hind-limb, the two lateral ones though nailed

being much shorter than the middle three. It has a "long pig-like snout,"

and the tail is cylindrical as in most other Jerboas, with a tuft of longer

hairs at the end. The incisor teeth, grooved in _Dipus_, are here smooth,

as in _Alactaga_. The species was probably obtained "in the sandy plains

round the city of Yarkand." {486}

_Alactaga_ is much like _Euchoreutes_; it has five toes, a cylindrical

tufted tail, the hairs at the end distichous, smooth incisors, and a

premolar present in the upper jaw. It also differs from _Euchoreutes_ by

the much smaller auditory bulla as well as in the fact that the

infra-orbital foramen has no separate passage for the nerve, which passage

is to be distinguished in both _Dipus_ and _Euchoreutes_. The best-known

species is the Siberian Jumping Rabbit, _A. jaculus_. Beneath the ends of

the three main toes of the feet are remarkable fan-shaped pads. In _A.

decumana_ the body and tail measure 7 and 10 inches respectively, the ears

2 inches. _Platycercomys_, a fourth genus of the family, is much less known

and is to be differentiated from the last three genera by the fact that it

has no premolars at all, the grinding tooth formula being thus 3/3. The

tail too is flattened and "lancet shaped." It extends from Siberia to

Nubia, and thus just enters the Ethiopian region.

The above are the more typical Jerboas. There remain several forms which

are not at all Jerboa-like in their way of life, but are nevertheless, on

anatomical grounds, placed with them. _Zapus_, an American genus, with the

exception of one Palaearctic species, is transitional in that its hind-legs

are rather long, but there is not so much difference between them as in the

typical Dipodidae. _Sminthus_ is at the opposite extreme to _Dipus_. Its

feet are short and of equal length; it climbs in trees, and may perhaps be

looked upon as nearest of all Dipodidae to the ancestral form of the group.

FAM. 8. PEDETIDAE.--The genus _Pedetes_ contains but one species, _P.

caffer_, the Cape Jumping Hare. The animal suggests a large Jerboa in

appearance on account of its jumping habits, the long hind-limbs, and the

long tail. The length of a fair-sized example is some 17 inches, with a

tail of the same length. The eyes and ears are large. The hands are

five-fingered and the feet only four-toed, the hallux being of course the

absent digit. In the skeleton it is interesting to note that the second and

third cervical vertebrae are so close together that there can be no free

movement; interesting because in _Dipus_ the cervicals are actually

ankylosed. The dorsal vertebrae are twelve. The small intestine is long,

measuring 7 feet 4 inches, while the caecum is short, being only 8 inches

long. The large intestine is 3 feet 10 inches long. The gall-bladder

appears to be {487} absent,[352] an exceptional state of affairs in

Rodents. A singular fact in the anatomy of this animal is the existence of

a septum dividing the lower part of the trachea. This is sometimes met with

in birds. As might be supposed from its large eyes, the Spring Haas, as the

animal is sometimes called, is nocturnal. Its long hind-limbs permit it to

leap enormous distances. It is a burrowing Rodent.

SECTION 3. HYSTRICOMORPHA.

FAM. 1. OCTODONTIDAE.--The Rodents of this family are of small to moderate

size, the only, relatively speaking, giant in the family being the

"Water-Rat," _Myocastor_. The toes are with but one exception not reduced;

the tail is long in the majority of the genera. The teats are placed high

up on the sides of the body. The clavicle is fully ossified. All the genera

are South or Central American in range with the exception of

_Petromys_.[353]

SUB-FAM. 1. OCTODONTINAE.--_Octodon_ has four species, which are all

Chilian, Peruvian, and Bolivian in distribution. The Degu, _O. degus_, has

a length of 160 mm., with a tail 105 mm. long. The ears are 18 mm. long. At

the roots of the claws are longish and stiff hairs which appear to serve as

"combs." The tail has long but sparsely scattered hairs. There are twelve

pairs of ribs. The lengths of the various sections of the intestine are as

follows: small intestine, 680 mm.; caecum, 90 mm.; large intestine, 390 mm.

These animals live in large companies. Closely allied is the genus

_Habrocoma_ (more correctly, as it appears, to be written _Abrocoma_), with

two species. _H. bennetti_ is 204 mm. long, with a tail of 103 mm. The ears

are long, 22 mm. The fore-feet have no outward trace of the thumb. Stiff

hairs like those that characterise _Octodon_ are found also in this genus.

The fur is very soft. The furring of the tail is much thicker than in

_Octodon_.

_Spalacopus_ with but a single species, _S. poeppigi_, is a burrowing

animal, from which indeed, and on account of its resemblance to _Spalax_,

it has received its name. The ears in accordance with the underground life

are short, only 5 mm. in length in an {488} example of 120 mm. The tail too

is reduced, being in the same example only 42 mm. in length. As in the last

two genera the large intestine is about one half of the length of the small

intestine.

The "Tuco-tuco," genus _Ctenomys_, has also short ears and tail. The claws

of the fore-feet are longer than those of the hind-feet.

A related form is _Aconaemys_ (better known as _Schizodon_), with similar

external characters; it inhabits high localities on the Andes.

_Petromys_ is the only genus of the sub-family which is not American in

habitat. It is an African form and there is but one species. Its anatomy

conforms to that of the genera already considered. The main difference in

structure is shown by the teeth. Their surface is uneven, and differs from

that of other Hystricomorphs "in that the enamel to the inside of each

upper jaw-tooth and outside on each lower jaw-tooth forms two tubercles, to

which correspond grooves in the reverse position of the applied teeth."

SUB-FAM. 2. LONCHERINAE.--The genus _Echinomys_ with thirteen species

belongs to the Neotropical region. The members of the genus are entitled

"Spiny Rats" since they have spines mixed with the fur. The tail is long

and the ears are very well developed. Both feet are five-toed. The tail is

scaly as well as haired. _Trichomys_ (also called _Nelomys_) is very close

to the above, and is also from the same part of the world.

The genus _Cannabateomys_ contains but one species, _C. amblyonyx_, which

was formerly included in the genus _Dactylomys_, but has lately been

separated by Dr. Jentink.[354] The animal is Brazilian and has a total

length of 520 mm., of which 320 mm. belong to the tail. It is a climbing

rat, and in accordance with that way of life has undergone some

modifications. The fore-feet are four-toed, the two middle toes being

markedly longer than the outer ones. The hind-feet are five-toed with the

same greater development of the two middle toes. The claws are small and

somewhat nail-like.

_Dactylomys_, also Brazilian, and with but one species, _D. dactylinus_,

differs from the last in the fact that the molars are simpler in form; they

are divided into two lobes, each of which {489} has but a single enamel

fold, whereas in _Cannabateomys_ these teeth have several enamel folds. The

tail, moreover, is but slightly hairy.

_Loncheres_ with eighteen species is another Neotropical genus allied to

the foregoing. Small spines are, as in many of these genera, intermingled

with the fur. This genus has as many as seventeen dorsal vertebrae, which

is an unusually large number. _L. guianae_ is known as the "Porcupine Rat."

Allied genera, also South American, and without spines in their fur, are

_Mesomys_, _Cercomys_, and _Carterodon_.

The South American _Thrinacodus_ is also known by one species,[355] _T.

albicauda_, which has rather more than the distal half of the long tail of

a white colour. The fore-feet have four toes. The ears are broad and short.

SUB-FAM. 3. CAPROMYINAE.--A third sub-family of the Octodontidae is formed

by the genera _Myocastor_, _Capromys_, _Plagiodontia_, and _Thrynomys_,

which are all Neotropical forms with the exception of the last, which is

African.

_Thrynomys_ (better known perhaps as _Aulacodus_) is a genus of African

Rodent, containing some four species. The best-known of these is _T.

swindernianus_, the Ground-Rat of West and South Africa. Its structure has

been investigated by Garrod,[356] by Tullberg,[357] and by myself.[358] The

fur is mingled with flattish bristles; the tail is moderately long, about

half as long as the body. The fore-feet are five-toed, but the two toes at

each end of the series are quite small. The hind-feet are only four-toed,

the hallux being absent. The claws of the hind-feet are stronger than those

of the fore-feet. The ears are not long. The limbs are decidedly short,

hence the name of "Ground-Pig" sometimes applied to this animal. The molars

are four in number in both jaws. The incisors of the upper jaw are twice

grooved. There are thirteen dorsal vertebrae. The length of the small

intestine is 60-1/2 inches, that of the large 49; the caecum is short,

being only 8 inches long. It is a remarkable fact that the acromion is

joined to the rest of the spine of the scapula by a joint.

_Myocastor_, a name which seems to have the rights of priority over the

more familiar _Myopotamus_, applies to a large South American aquatic

Rodent. The general aspect of the animal {490} suggests a Water-Rat of

large size (it has been exhibited in shows as a phenomenal product of

London sewers!); the tail is nearly as long as the body. The ears are

small. The limbs are short. The tail is naked. The hind-feet are webbed,

but not so much so as in _Hydromys_. A small thumb is present. The animal

has thirteen pairs of ribs; the molars are four in each jaw. The large

intestine is more than three times the length of the small, and the caecum

is, as in the last genus, relatively short.

_Capromys_ is a genus[359] which is remarkable on account of its restricted

distribution. It is found only in the islands of Cuba and Jamaica. There

are four species, of which _C. melanurus_ is a dark brown-coloured animal

with a blacker tail, nearly as large as a Rabbit. The native name of this

Rodent is "_hutia_." It is also remarkable for having a stomach more

complicated than is the rule among the mammals of this group. The organ is

divided by two constrictions into three compartments. In _C. pilorides_ the

liver is occasionally divided up in an extraordinary fashion into small

lobules. _Capromys_ has the large number of sixteen dorsal vertebrae.

FAM. 2. CTENODACTYLIDAE.--For these African genera it seems admissible to

form a distinct family, though Thomas, and Flower and Lydekker, only allow

to the genera _Ctenodactylus_, _Pectinator_, and _Massoutiera_ sub-family

rank. On the other hand, Tullberg removed these genera entirely from the

Hystricomorph section and placed them as a section of the sub-tribe

Myomorphi of the tribe Sciurognathi. It was chiefly the form of the

mandible which led to this placing, for in these Rodents, as in all

Squirrel- and Rat-like Rodents, and unlike what is found in the

Hystriciform genera, the angular process of the mandible is not bent

sideways.

The genus _Ctenodactylus_ derives its name from the peculiar strong

bristles which form a comb-like structure upon the hind-feet and hide the

claws; these are stated to be for the purpose of dressing the fur. The

Gundi of North Africa, _C. gundi_, has a length of 190 mm., with a short

tail of 17 mm. The ears are only moderate in size. The dental formula of

the molars is 4/3. The incisors are white. The feet have four digits, and

the hind-limbs are the longer. The large intestine is distinctly longer

than the small intestine. {491}

_Pectinator spekii_ is the only representative of a genus not far removed

from _Ctenodactylus_; it is a smallish Rodent, 6 inches in length,

exclusive of a rather bushy tail nearly 3 inches long. It comes from

Abyssinia. It has somewhat the appearance of a Squirrel, which is

heightened by the fact that when sitting the tail is arched over the back;

when running the tail is carried out straight. There are only four toes

visible externally on both fore- and hind-limbs, but pollex and hallux

exist in the skeleton, with a single phalanx each. There is only a single

pair of mammae, and in correspondence with this but two or three young are

produced at a time. The hind-feet have bristles very much like those of

_Ctenodactylus_. The molars, however, are 4/4. There are twelve ribs, of

which six reach the sternum. The latter is made up of six pieces, and the

manubrium in its breadth anteriorly suggests that of the Vizcachas. The

clavicles are present.[360]

[Illustration]

FIG. 240.--Carpincho. _Hydrochoerus capybara._ x 1/12.

FAM. 3. CAVIIDAE.--This family, which includes the Cavies and the Capybara,

is entirely South American and West Indian in distribution. It embraces

animals of fair to large size, the Capybara {492} (or Carpincho) being the

greatest of existing Rodents. The ears are well developed. The toes are

commonly reduced, and the members of this family possess only a rudimentary

tail. The hair though rough is not spiny. Other characters had best be

deferred until the several genera are treated of. We shall begin with the

giant of the family, the genus _Hydrochoerus_. This genus contains but a

single species, _H. capybara_ of South America. It reaches a length of some

4 or 5 feet. The ears are not large; the tail is completely absent. The

fore-feet are four-toed, the hind-feet three-toed; the digits are webbed,

though not to a very great degree, and the nails have the appearance of

hoofs. There are fourteen dorsal vertebrae; the clavicle is absent. In the

skull the paroccipital processes are of great length. The infra-orbital

foramen is large. The most remarkable fact about the teeth is the great

size of the posterior molar of the upper jaw; it has fourteen folds of

enamel, more than all the anterior teeth possess collectively. The incisors

are white and grooved in front. The measurements of the alimentary tract as

given by Tullberg are: small intestine, 4350 mm.; caecum, 450 mm.; large

intestine, 1500 mm.

[Illustration]

FIG. 241.--Patagonian Cavy. _Dolichotis patachonica._ x 1/10.

The Capybara or Carpincho is largely aquatic in its habits. Their

"favourite locality," writes Mr. Aplin,[361] "is a broad laguna {493} in

the river, furnished with open water, and also beds of 'camelotes,'--a

sloping open grassy bank on one side, where the Carpinchos can lie in the

daytime in the cooler weather, sleeping and basking in the sunshine; on the

other a low shelving bank, clothed with 'Sarandi' scrub growing out into

the black reeking mud and shallow water beyond." They always take to the

water when alarmed, at a rate and with a gait which reminded Mr. Aplin of a

Pig. When in the water they swim slowly with the upper part of the head,

including nose, eyes, and ears, above the surface. But they can dive for a

considerable time and distance, and baffle their enemies by seeking the

shelter of a mass of water-plants, and lying there with their noses only

just above the surface.

The genus _Dolichotis_[362] has long ears, and generally resembles a rather

long-legged Hare in appearance. The front-feet are four-toed, the hind

three-toed. The Patagonian Cavy, as this animal is called, has twelve

dorsal vertebrae, and rudimentary clavicles.[363] The paroccipital

processes are long; the incisors are white, and are not grooved in front.

The sternum has six pieces, and seven ribs reach it.

_Cavia_, including the species _C. porcellus_, the Guinea-pig (which name

is a corruption apparently of Guiana pig), has the same number of toes on

its hind- and fore-feet as has the Capybara. The name applied to the wild

stock whence our Guinea-pig is derived is the Restless Cavy. The fur is

greyish; of the domestic animals the colour is too well known to need

description.

FAM. 4. DASYPROCTIDAE.--The genus _Coelogenys_ includes but two species.

_C. paca_, known as the "Spotted Cavy" or "Paca," has a brown body, with

white spots like those of a Dasyure; it is one of the largest of Rodents,

and has a quite short tail. The hand and foot are both provided with five

digits; but the thumb is small, and in the foot the three middle toes

considerably exceed the others in length. The hind-foot is practically

three-toed. The fibula is not nearly so reduced as in _Dolichotis_. The

skull of the animal is remarkable for the extraordinary development in

breadth of the jugal arch, which is sculptured externally. There is a large

cavity formed below, at the maxillary end of this huge {494} arch, by the

curving inwards of the bone, which lodges a cavity continuous with the

mouth. The palate has anteriorly a ridge on either side, and is thus

divided from the sides of the face in a way which is not found[364] in the

allies of _Coelogenys_. Clavicles are present. There are thirteen dorsal

vertebrae. The incisors are coloured red in front. The animal is South

American, and in that continent is limited to the Brazilian sub-region.

This, the best-known species of Paca, is called the Gualilla by the natives

of Ecuador; in the same district another form is met with which the natives

term Sachacui (signifying Forest Cavy). It is very often the case that a

different native name expresses a real specific difference; and to the

latter form M. T. Stolzmann has given the name of _C. taczanowskii_.[365]

This form, unlike the common Paca, which is fond of forests and low-lying

ground in the neighbourhood of water, is alpine in habitat, living upon

mountains of 6000 to 10,000 feet. It burrows in much the same way as its

congener, and is greatly sought after as food, its meat possessing an

"exquisite taste." It is pursued by dogs, by whose aid one of the two

entrances to the burrow is guarded, and the creature is smoked out and

killed with a stick.

The genus _Dasyprocta_, containing those Rodents known as Agoutis, is

divisible into several species, apparently about twelve, all of which are,

like the Pacas, confined to the Neotropical region. They have, however, a

much wider range within that region, and occur as far north as in Central

America and in some of the West Indian Islands. They are of rather smaller

size than the Paca, and are without spots. The colour is of a golden brown

in some forms, but usually has a freckled, grizzled, greenish kind of

appearance. The tail is stumpy, the hind-limbs are distinctly longer than

those of the Paca, and the two lateral toes have disappeared from the

feet--a concomitant as it seems of the Agouti's greater powers of running.

The three metatarsals are closely pressed together, and the foot is as it

were on the way towards the highly-modified foot of the Jerboa. The

fore-feet are, however, five-toed. The clavicle is rudimentary,[366]

whereas it is well developed in the Paca. The skull has not the peculiar

modifications of that of the last-mentioned type. The sternum has seven

{495} pieces, and eight ribs reach it. A curious difference between this

genus and the last is in the relative proportions of the regions of the

intestine. The figures given by Tullberg for the two animals are--for

_Coelogenys_, small intestine, 4800 mm.; caecum, 230 mm.; large intestine,

21,000 mm.;--for _Dasyprocta aguti_ the same author gives: small intestine,

4200 mm.; caecum, 200 mm.; large intestine, 1000 mm. The Agouti, says Mr.

Rodway,[367] is as wily as the Fox. "If chased he will run along the

shallows of a creek to hide his scent from the dogs, or swim over and back

again several times for the same purpose. He never runs straight when

pursued, but doubles, often hiding until a dog has passed, and then making

off in a different direction. Like the fox he has been hunted for a very

long period, and, like Reynard, has grown wiser with every generation."

[Illustration]

FIG. 242.--Agouti. _Dasyprocta aguti._ x 1/10.

FAM. 5. DINOMYIDAE.--The genus _Dinomys_ of Dr. Peters[368] is a very

little known and remarkable form from South America allied to the Capybara,

the Chinchilla, and other South American Rodents. It is only known by a

single example found wandering about a courtyard in a town of Peru. It is

externally like, and of about the same size as the Paca, but has a hairy

tail. The animal is four-toed and plantigrade; the ears are short, and the

nostrils are [369]-shaped. It is usually regarded as belonging {496} to a

separate family which will include but the one species, _D. branickii_.

FAM. 6. CHINCHILLIDAE.--This family, likewise South American, contains

three genera,[370] all of which agree in having long limbs, especially the

hind-limbs, and a bushy and well-developed tail. The hair is exceedingly

soft, hence the commercial value of "chinchilla."

The genus _Chinchilla_, containing but a single species, _C. laniger_, is a

small and squirrel-like creature, living at considerable heights in the

Andes. The eyes, as it is a nocturnal creature, are naturally large; and so

also are the ears. The fore-feet have five toes, the hind-feet only four;

they are furnished with feeble nails. The innermost toe of the hind-foot

has a flat and nail-like claw. There are thirteen dorsal vertebrae, and the

long tail has more than twenty. The clavicle is well developed, as in the

other genera of this family. The large intestine of this animal is

extraordinarily long; the proportions of the different regions of the gut

are shown by the following measurements: small intestine, 820 mm.; caecum,

125 mm.; large intestine, 1340 mm. Such a disproportion between the large

intestine and the small, to the advantage of the former, is a very strange

fact in the anatomy of this Rodent.

The genus _Lagidium_ (also called _Lagotis_), which includes "Cuvier's

Chinchilla," is also a mountain dweller. There are several species of this

genus, which differs from _Chinchilla_ by the complete abortion of the

thumb and of the great toe. The intestinal proportions are those of

_Chinchilla_. The ears and tail are long. _L. cuvieri_ measures 1-1/2 feet

in length.

_Lagostomus_, again, has but one species, _L. trichodactylus_. The animal

has a tail about half the length of the body. The digits are reduced as

compared with _Chinchilla_, there being but four on the fore- and three on

the hind-feet. There are only twelve dorsal vertebrae, and seven ribs reach

the sternum. In the skull a distinguishing mark from the last two genera is

the separation of the infra-orbital foramen into two by a thin lamella of

bone. The large intestine is between one-half and one-third the length of

the small intestine, and thus differs much from that of _Chinchilla_. {497}

[Illustration]

FIG. 243.--Vizcacha. _Lagostomus trichodactylus._ x 1/10.

The Vizcacha lives in societies of twenty to thirty members,[371] in a

"village" ("Vizcachera"), a dozen or so of burrows, which intercommunicate.

They lie at home during the day and come out in the evening. Their burrows,

like those of the Prairie Marmot, harbour other creatures, which apparently

live on amicable terms with the Vizcachas; such are the burrowing owl, a

small swallow, and a _Geositta_. The Fox also affects these burrows, but

then he ejects the rightful owner of the particular burrow which he

selects. When the young Foxes are born the vixen hunts the Vizcachas for

food. The Vizcacha has a most varied voice, producing "guttural, sighing,

shrill, and deep tones," and Mr. Hudson doubts if there is "any other

four-footed beast so loquacious or with a dialect so extensive." These

animals are very friendly, and pay visits from village to village; they

will attempt to rescue their friends if attacked by a Weasel or a Peccary,

and to disinter those covered up in their burrows by man.

FAM. 7. CERCOLABIDAE.--A number of the characters which differentiate this

family from the Hystricidae or Ground Porcupines of the Old World are given

under the description of the latter. The principal external characters are

the prehensile tail, the admixture of spines with hairs, and the nature of

the sole of the foot. In these points the New-World Cercolabidae differ

from the Old-World Hystricidae. It is interesting to notice that {498} in

both families we have long-tailed and short-tailed forms. _Cercolabes_

corresponds to _Atherura_ or _Trichys_, and _Erethizon_ to _Hystrix_.

The genus _Erethizon_, the "Urson" of Canada, has a short, stumpy tail. Its

spines are almost hidden by enveloping hair. The fore-feet have four, the

hind-feet five toes. The short tail of this creature is remarkable when we

reflect upon its climbing habits. It appears, however, to be a weapon with

which it strikes sideways at the enemy.

[Illustration]

FIG. 244.--Brazilian Tree Porcupine. _Sphingurus prehensilis._ x 1/6.

Of the Neotropical genus _Cercolabes_ (sometimes called _Sphingurus_,

_Synetheres_, or _Coendou_) there are some eight or nine species, all found

in Central and South America. The animal is arboreal, and has in

correspondence with that habit a prehensile tail. The spines are not so

stout as in the Ground Porcupines, and are often coloured yellowish or

reddish. In correlation with its tree-frequenting habits the bones of

_Cercolabes_ show certain differences from those of the Ground Porcupines.

The scapula is broader and rounder in front than is that of _Hystrix_; the

phalanges of the thumb (which is rudimentary) are fused together as in the

Canadian _Erethizon_; but those of the very small hallux are also fused,

whereas in _Erethizon_, as in _Hystrix_, they are separate. In one species,

_C. insidiosus_, Sir W. Flower states that there are as many as seventeen

dorsal vertebrae and thirty-six caudals. The tail is thus very long. In _C.

villosus_ there are fifteen dorsals and twenty-seven caudals; eight ribs

reach the sternum, which is composed of seven pieces, the {499} sixth being

very small. The clavicles are well developed. A curious fact about _C.

villosus_ is that the acetabular cavity is perforate (on both sides), or at

least only closed by membrane. In many forms of Rodents the bone is very

thin in this region. This fact perhaps lessens the significance of the

perforation of the acetabulum of _Echidna_ (see p. 109).

Of the allied genus _Chaetomys_, also Neotropical, there is but a single

species, which inhabits Brazil. It has a nearly completely closed orbit, a

feature which differentiates it from the last animal, and one which also

shows it to be a more modified form. The spiny covering is less pronounced

than in its allies.

FAM. 8. HYSTRICIDAE.--This family is characterised by the fact that all its

members possess spines; but the tail, if at all long, is not prehensile,

and the soles of the feet are smooth and not covered with rough tubercles,

as in the Tree Porcupines of the next family, Erethizontidae. The clavicle

is less developed than in the arboreal forms. In the organs of digestion

there are points of a family difference between the two groups of spiny

Rodents. The tongue has serrated scales arranged in transverse rows, which

are directed backwards. A gall-bladder, though not always present, is

sometimes found; it apparently never exists in the arboreal Porcupines and

in _Erethizon_. The lungs show a great tendency to subdivision, which

appears to be especially marked in the genus _Atherura_. The caecum seems

also to be shorter in the Ground Porcupines. In _Hystrix cristata_ the

small intestine measures 15 feet 7 inches; the caecum, 8 inches; the large

intestine, 4 feet 4 inches:--in _Atherura africana_ the caecum measures

7-1/2 inches; the large intestine, 1 foot 10 inches. The corresponding

measurements of _Synetheres villosus_ were: small intestine, 7 feet 3

inches; caecum, 1 foot 4 inches; large intestine, 2 feet 7 inches. In

_Erethizon_ the caecum is 2 feet 4 inches in length. These differences are

too large and too constant in a number of presumedly allied forms to be

overlooked.

Mr. Parsons has directed attention[372] also to a number of muscular

differences, such indeed as might be expected to occur between animals of

such different habits.

The genus _Hystrix_ embraces the better-known Porcupines. It is a genus of

wide range, extending from the East Indies to Africa, {500} and even

occurring in Europe. There are several species, of which the common

_Hystrix cristata_ is the best known, and is the one which is to be found

in Europe.

[Illustration]

FIG. 245.--Common Porcupine. _Hystrix cristata._ x 1/10.

The spines of the common form and of the others are solid in the middle of

the body, but on the tail they are expanded into hollow quills, which make

much rattling. They are as a rule black and white, the middle of the spine

being banded with black. A great crest of coarse long hairs on the head is

responsible for the scientific name of the well-known form. Sometimes in

this genus, as in the Tree Porcupines of Brazil, the spines are orange or

yellow; but it is said that the colour is soon lost in this country. As a

matter of fact it is the easiest thing in the world to wash out with

ordinary tap-water much of the yellow colour of the spines of the South

American _Sphingurus_. The same may be the case with the pigment of the

Old-World Porcupines. There are fourteen to fifteen dorsal vertebrae and

four or five lumbars. The tail varies in length, but is shorter than the

long tail of the arboreal New-World forms. It seems impossible when

mentioning the Porcupine to escape from some observations about its alleged

habit of shooting its quills. For some reason or other Buffon has got the

credit of inventing, or at {501} least promulgating, this legend, which has

even grown so in the telling that the quills are said to be capable of

penetrating planks of wood. What Buffon said _apropos_ of this matter is,

"The marvellous commonly is pleasingly believed, and increases in

proportion to the number of hands it passes through." It is of course the

rattling of the spines and the occasional falling out of loose ones which

has started the legend. They are, however, excellent weapons of offence,

and the animal charges somewhat backwards to make the best use of them

against the foe. The spines, however, are by no means an absolute

protection, since, as Mr. Ridley informs us,[373] Tigers will kill and eat

these animals just as the Thylacine is apparently indifferent to the spiny

armature of _Echidna_.

Of the Brush-tail Porcupine, _Atherura_[374] there are at any rate two

species, the West African _A. africana_ and the Malayan _A. fasciculata_.

It is interesting that the gap in the present distribution is partially

filled by the discovery of fossil teeth near Madras. The genus does not

differ widely in external appearance from _Hystrix_; it has, however, a

rather longer tail; there are fewer large spines, and there is a tuft of

them at the end of the tail, whence is derived the name of the genus. The

frontal bones project a little distance between the nasals, a feature which

does not seem to appear in the true Porcupines. There are fourteen dorsal

vertebrae and five lumbars. The twenty-four caudal vertebrae of this

Porcupine shows how much longer is its tail than that of _Hystrix_; for in

the latter twelve is about the number.

A third genus of Old-World Porcupine is the singular _Trichys_.[375] Of

this there is but one species, _T. lipura_. It is a curious fact that out

of three examples, all from Borneo, two were quite without a tail. But this

appears to be merely a mutilation, though it is singular that the natives

state it to be without a tail. One cannot help thinking of the way in which

lizards sometimes shed their tails when pecked at. The tail of this genus

is more than half the length of the body and head. _Trichys_ has sixteen

dorsal and six lumbar vertebrae. There is a tuft of quills at the end of

the tail, which are thin and compressed, {502} though truncate at the free

extremity and hollow; they represent in a more rudimentary way the much

stronger tuft at the end of the tail of other Porcupines. It is a curious

fact that this and other Porcupines possess a mechanism for warning their

foes precisely comparable to that of the rattlesnake. There are sixteen

dorsal vertebrae.

SUB-ORDER 2. DUPLICIDENTATA.

The chief feature of this group is the existence of two pairs of incisor

teeth in the upper jaw, of which the inner are very small and lie behind

the outer. In the skull the infra-orbital foramen is small; the incisive

foramina are very large. The tail is short or absent.

FAM. 1. LEPORIDAE.--This family is distinguished from the Lagomyidae by the

long ears, by the tail, which is present, though short, and by the longer

limbs. There are six teeth belonging to the molar series in the upper jaw,

and five of the same in the lower. The clavicle is imperfect.

The longest known genus of this family, _Lepus_, was, until the quite

recent discovery of _Romerolagus_, the only genus. It is of universal

range, excepting Australasia and Madagascar, and consists of about sixty

species. These are the Hares and Rabbits, to the former being assigned the

longer-limbed forms.

As every text-book of zoology contains a more or less elaborate account of

the structure of the Common Rabbit, and as there is but little structural

difference between the members of the genus, a short account of the generic

peculiarities of _Lepus_ will suffice here. The fore-feet are five-toed,

the hind-limbs four-toed. The hairy integument enters the mouth cavity, and

the inside of the cheeks have a hairy covering. The soles of the feet are,

moreover, hairy. The maxillary bones are curiously sculptured.

[Illustration]

FIG. 246.--_Lepus cuniculus._ Skull. A, Lateral view; B, ventral view.

_ang.pro_, Angular process of mandible; _as_, alisphenoid (external

pterygoid process); _aud.me_, external auditory meatus; _b.oc_,

basioccipital; _b.sph_, basisphenoid; _cond_, condyle; _cor_, coronoid

process; _fr_, frontal; _int.pa_, inter-parietal; _ju_, jugal; _lcr_,

lachrymal; _max_, maxilla; _nas_, nasal; _opt.fo_, optic foramen; _o.sph_,

orbitosphenoid; _pa_, parietal; _pal_, palatine; _pal.max_, palatine plate

of maxilla; _pal.p.max_, palatine process of premaxilla; _par.oc_,

paroccipital process; _peri_, periotic; _p.max_, premaxilla; _pt_,

pterygoid; _p.t.sq_, post-tympanic process of squamosal; _s.oc_,

supraoccipital; _sq_, squamosal; _ty.bul_, tympanic bulla; _vo_, vomer;

_zyg.max_, zygomatic process of maxilla. (From Parker and Haswell's

_Zoology_.)

The Common Rabbit, _L. cuniculus_, differs from the Common Hare in the

comparatively shorter ears and legs. The ears have not, to so marked a

degree, the black tips of those of the Hare. The animal, moreover, produces

naked young, and lives in burrows of its own excavation. A difference in

the structure of the caecum, which distinguishes the Rabbit from the Hare,

has been {504} pointed out by Professor W. N. Parker.[376] These

differences have led some to approve of its separation from the Hares into

a genus _Oryctolagus_. This animal is believed to be an introduced species,

and to have been brought by man into these islands. Its original home is

the Spanish Peninsula, the south of France, Algiers, and some of the

Mediterranean islands. Mr. Lydekker thinks that the only other species of

_Lepus_ which can be considered to be a "Rabbit" is the Asiatic _L.

hispidus_.

Of Hares there are two species in this country. The Common Hare, _L.

europaeus_ (the name _L. timidus_ seems to be really applicable to another

species to be referred to presently), extends all over Europe excepting the

extreme north of Russia and Scandinavia. It is not known in Ireland, and,

curiously enough, attempts to acclimatise this animal in that island have

failed--a state of affairs which contrasts with the fatal ease with which

the Rabbit has been introduced into Australia. Ireland has, however, the

Variable Hare, _L. timidus_ (also called _L. variabilis_), a species which

is common in other parts of Europe, and which extends as far east as Japan.

This species differs from its ally by the fact that it often turns white in

winter with the exception of the black tips to the ears. In Ireland this

change does not always occur; but Mr. Barrett-Hamilton has commented upon

the fact that Hares of this species do change on Irish mountains. It

appears that in this animal the change from the winter to the summer dress

is accomplished by the actual casting off of the white hairs and their

replacement by a fresh growth of "blue" hairs. A similar change occurs in

the American _L. americanus_.

Dr. Forsyth Major has noted the fact that the various species of Hares can

be distinguished by the condition of the furrows upon the upper incisors.

Thus two African species, _L. crawshayi_ and _L. whytei_, are to be

separated by the fact that in the former the incisors are quite flat,

whereas in _L. whytei_ the groove is more prominent and there is a second

shallow furrow.

The genus _Romerolagus_[377] is quite a recent discovery. It occurs on the

slopes of Popocatepetl in Mexico; it has the general aspect of the last

genus, and is spoken of as a "Rabbit." It inhabits runs in the long grass

which clothes the sides of the {505} mountain. Externally it is something

like the Pikas, since it has no tail visible. The ears, too, are short, and

the hind-legs comparatively short. The skull is very like that of the

Rabbit; but in other osteological details it is aberrant. Thus the clavicle

is quite complete, and only six ribs articulate with the sternum, instead

of the seven that we find in the Rabbit.

FAM. 2. LAGOMYIDAE.--The animals of this family are smaller than the Hares

and Rabbits; they have short Vole-like ears and no external tail. The limbs

also appear to be shorter. As there is but a single genus, the characters

of the family may be described in connexion with those of the genus, which

is known as _Lagomys_ (apparently more correctly _Ochotona_). Of this genus

there are about sixteen species, which are mainly Asiatic; one species

extends its range into Eastern Europe, and three are North American.

The skull has not the supra-orbital grooves of the Rabbits, and has a

well-marked backward process of the zygomatic arch. There are eighteen

dorsal vertebrae. The molars and premolars are five.

The vernacular names of "Pika" and "Piping Hares" have been applied to the

members of this genus, the latter on account of their peculiar call. They

live among rocks in companies and they burrow. They are usually found at

considerable altitudes: thus _L. roylei_, the "Himalayan Mouse Hare," is

found at elevations as high as 16,000 feet; while _L. ladacensis_ gets even

higher, 19,000 feet having been recorded. With the habits of a Marmot, so

far as concerns living in burrows and at great altitudes, the animals of

this genus, with their squat form and short ears, are not unlike those

animals. In the past this genus occurred more generally over Europe.

Species from Miocene beds have been met with in England, France, Germany,

and Italy.

FOSSIL RODENTS.--Quite a large number of existing genera of Rodents are

known from even the earlier strata of the Tertiary period. The Squirrels

(and even the genus _Sciurus_ itself) occur in the Upper Eocene. So, too,

do the genera _Myoxus_, and (in South America) _Lagostomus_.

_Spermophilus_, _Acomys_, _Hystrix_, _Lagomys_, _Lepus_, _Hesperomys_ are

known from Miocene rocks. _Rhizomys_, _Castor_, _Cricetus_, _Mus_,

_Microtus_, and some others appear to have originated so far as we know in

the Pliocene, while a still larger series of existing genera are

Pleistocene. It is interesting {506} to note that some of the extinct

genera were much larger than recent forms. At present, _Hydrochoerus_ is

the biggest Rodent; but the genus _Megamys_ from the Pampas formation of

Argentina was "nearly as large as an ox." The wider range of genera in the

past is illustrated by _Hystrix_, which, now an Old-World form, is

represented by remains in the Miocene and Pliocene of America.

It is a significant fact that of living genera _Sciurus_ is the oldest; for

it has been pointed out that in a number of features the Squirrels are

among the most primitive of Rodents. The zygomatic arch is slender, and has

thus not acquired the specialisation that is to be found in that part of

the skull in other Rodents; moreover, the "jugal bone is not supported by

any process from the maxilla exactly as in the primitive Ungulata." The

feet, too, are unspecialised, though that is the case with many other

genera. It may also be pointed out that the teeth bear not a little

likeness to those of _Ornithorhynchus_ in their multituberculate character.

Some few fossil forms have already been dealt with in the preceding pages.

The two genera _Castoroides_ and _Amblyrhiza_, from the Pleistocene of

North America and the West Indies, are usually regarded as forming a

family. The skull of the former genus indicates an animal of the size of a

Bear. It is compared to that of _Castor_, but it has a wide infra-orbital

foramen. The teeth are four in each jaw, and are formed of three to five

lamellae; the incisors of this animal are powerful but short. _Amblyrhiza_,

on the other hand, has long incisors which are longitudinally grooved

anteriorly. It has a free fibula. This latter as well as other characters

have led Tullberg to remove it from association with _Castoroides_.

ORDER X. TILLODONTIA.

This group of Eocene mammals is to be defined by a number of characters, of

which the more important are the following:--The incisors are enlarged,

grow from persistent pulps, and are coated with enamel upon the outer

surface only; they are those of the second pair only, the first and third

having disappeared or become small. The canines are reduced in the later

forms. {507}

[Illustration]

FIG. 247.--_Tillotherium fodiens._ Left lateral view of skull. (From

Flower, after Marsh.)

These animals have been regarded as ancestral Rodents, to which the tooth

characters just mentioned clearly show likenesses. The earliest known form

is _Esthonyx_. This genus shows such primitive characters, compared with

its later representatives, as the existence of all three pairs of incisors

in the upper jaw, but only two in the lower jaw. The enlarged incisors of

both jaws do not seem to have grown from persistent pulps.

_Anchippodus_, a later form, still preserves the upper pair of first

incisors in a vestigial form; the strong second incisors grew from

persistent pulps. The most recent genus, _Tillotherium_, shows the

characteristics of the group at their height. The strong Rodent-like,

chisel-shaped incisors, which are reinforced by a small additional pair in

the upper jaws only, are persistent. The grinding teeth are of the

tritubercular pattern; there are three of each kind in the upper jaw, but

in the lower jaw only two premolars on each side. This is at any rate the

case with some, while others have three. The canine, though present in both

jaws, is insignificant. As in many ancient types, there is an

entepicondylar foramen in the humerus. The feet were five-toed, and bore

sharp, laterally-compressed claws. The skull has been compared in general

aspect to that of a Bear.

* * * * *

{508}

CHAPTER XVI

INSECTIVORA--CHIROPTERA

ORDER XI. INSECTIVORA.

The Insectivora[378] are an order of mammals to which it is (to quote

Professor Huxley) "exceedingly difficult to give a definition." They are,

however, none of them large animals, and most of them are nocturnal in

habit--two circumstances which may have had something to do with their

survival from past ages, as may have also their modification to so many and

diverse modes of life; for everything points to the antiquity of the group.

They are, for instance, more or less plantigrade. The snout is generally

long, and is often prolonged into a short proboscis.[379] There is a

tendency for the teeth to be of a generalised type, and their number is

often the typical mammalian forty-four. Moreover, trituberculate teeth,

which are certainly an ancient form of tooth, are common; and indeed the

Insectivora of the southern regions of the globe, _e.g._ Centetidae,

Solenodontidae, and Chrysochloridae, have the most prevalent

trituberculism, a fact which is of importance in considering the age of the

animal life of these regions of the world. The limbs are, as a rule,

provided with five digits. The hemispheres of the brain are usually smooth,

and do not extend over the cerebellum. The palate is often fenestrate as in

the Marsupials, and as in that group the lower jaw is sometimes inflected.

But the latter character also occurs in the Sea-lions and elsewhere.

Clavicles are present, as a rule, but not in _Potamogale_. {509}

There is, furthermore, a distinct tendency towards a disappearance of

functional milk teeth, which is best seen in _Sorex_, where there are only

seven milk teeth, none of which ever cut the gum. This suppression of the

milk dentition is like that of the Marsupials, Edentates, and Whales, all

of which appear to be--the first certainly are--ancient forms of mammalian

life.

There is also a fairly well-defined, though shallow, cloaca in many genera.

Finally, the testes are purely abdominal in some, and in none is there a

full descent into a scrotum, as in the more highly-developed Eutheria.

SUB-ORDER 1. INSECTIVORA VERA.

FAM. 1. ERINACEIDAE.--This family contains the genera _Erinaceus_,

_Hylomys_, and _Gymnura_.

_Hylomys_, considered by Dobson to fall within _Gymnura_, is kept separate

by Leche.[380] _H. suillus_ is a Malayan animal, small in size, about 5

inches long, with a short tail. Like _Gymnura_ it is spineless. The ears

are decidedly large and nude. There is one pair of inguinal and one pair of

thoracic teats. The colour above is a rusty brown with yellowish-white

under parts. The palms and soles are quite naked. In its general form it

recalls _Tupaia_ very much more than its own immediate relatives. There is

no doubt, however, of its systematic position when the skeleton and teeth

are examined. A variety has been described from altitudes of 3000 to 8000

feet on Mount Kina Balu in Borneo. It has the complete dentition of

forty-four teeth. There are fourteen pairs of ribs. As in _Gymnura_ the

tibia and fibula are united below. The genus is considered by Leche to be

the oldest existing type of Erinaceidae.

_Gymnura_[381] is also a Malayan form with the complete dentition of the

last, but with fifteen pairs of ribs and a longer tail, consisting of

twenty-three vertebrae as against fourteen. There is, as with _Hylomys_,

but one species, _G. rafflesii_. This animal has a peculiar odour,

resembling decomposed cooked vegetables. {510} The under surface of the

tail is rough, and it is thought by Dr. Blanford that it may be of use to

the animal in climbing. Its compressed terminal third and the fringe of

stiff bristles on the under surface of this indicate, according to Dr.

Dobson, powers of swimming, or at any rate a not very remote ancestry of

swimming creatures. It is purely insectivorous in diet.

_Erinaceus_, including the Hedgehogs, is a widely distributed

genus--Palaearctic, Oriental, and Ethiopian in range. There are about

twenty species. The familiar spines distinguish the Hedgehogs from their

allies, as also the fact that they possess but thirty-six teeth, the

formula being I 3/2 C 1/1 Pm 3/2 M 3/3. There are fifteen or fourteen ribs,

and the tail is very short, consisting of only twelve vertebrae. As in

_Gymnura_ there is no caecum. The upper canine has usually, as in other

Erinaceidae, two roots, but not in _E. europaeus_, which is one of the most

modified of Hedgehogs.