THE SCYPHOPHORI, HAPLOMI, AND XENOMI
=ORDER Scyphophori.=—The _Scyphophori_ (σκύφος, cup; φορέω, to bear)
constitutes a small order which lies apparently between the _Gymnonoti_
and the _Isospondyli_. Boulenger unites it with the _Isospondyli_. The
species, about seventy-five in number, inhabit the rivers of Africa,
where they are important as food-fishes. In all there is a deep cavity
on each side of the cranium covered by a thin bony plate, the
supertemporal bone. There is no symplectic bone, and the subopercle is
very small or concealed. The gill-openings are narrow and there are no
pharyngeal teeth. The air-bladder connects with the ear, but not
apparently in the same way as with the _Ostariophysan_ fishes, to which,
however, the _Scyphophori_ are most nearly related. In all the
_Scyphophori_ the body is oblong, covered with cycloid scales, the head
is naked, there are no barbels, and the small mouth is at the end of a
long snout. All the species possess a peculiar organ on the tail, which
with reference to a similar structure in _Torpedo_ and _Electrophorus_
is held to be a degenerate electric organ. According to Günther, "it is
without electric functions, but evidently representing a transitional
condition from muscular substance to an electric organ. It is an oblong
capsule divided into numerous compartments by vertical transverse septa
and containing a gelatinous substance."
=The Mormyridæ.=—There are two families of _Scyphophori_. The
_Mormyridæ_ have the ordinary fins and tail of fishes and the
_Gymnarchidæ_ are eel-like, with ventrals, anal and caudal wanting.
_Gymnarchus miloticus_ of the Nile reaches a length of six feet, and it
is remarkable as retaining the cellular structure of the air-bladder as
seen in the garpike and bowfin. It doubtless serves as an imperfect
lung.
The best-known genus of _Scyphophori_ is _Mormyrus_. Species of this
genus found in the Nile were worshiped as sacred by the ancient
Egyptians and pictures of _Mormyrus_ are often seen among the emblematic
inscriptions. The Egyptians did not eat the _Mormyrus_ because with two
other fishes it was accused of having devoured a limb from the body of
Osiris, so that Isis was unable to recover it when she gathered the
scattered remains of her husband.
In _Mormyrus_ the bones of the head are covered by skin, the snout is
more or less elongated, and the tail is generally short and
insignificant. One of the most characteristically eccentric species is
_Gnathonemus curvirostris_, lately discovered by Dr. Boulenger from the
Congo. Fossil _Mormyridæ_ are unknown.
[Illustration:
FIG. 149.—_Gnathonemus curvirostris_ Boulenger. Family _Mormyridæ_.
Congo River. (After Boulenger.)
]
=The Haplomi.=—In the groups called _Iniomi_ and _Lyopomi_, the
mesocoracoid arch is imperfect or wanting, a condition which in some
cases may be due to the degeneration produced by deep-sea life. In the
eels a similar condition obtains. In the group called _Haplomi_ (ἁπλοός,
simple; ὤμος, shoulder), as in all the groups of fishes yet to be
discussed, this arch is wholly wanting at all stages of development. In
common with the _Isospondyli_ and with soft-rayed fishes in general the
air-bladder has a persistent air-duct, all the fins are without true
spines, the ventral fins are abdominal, and the scales are cycloid. The
group is a transitional one, lying almost equidistant between the
_Isospondyli_ and the _Acanthopterygii_. Gill unites it with the latter
and Woodward with the former. We may regard it for the present as a
distinct order, although no character of high importance separates it
from either. Hay unites the _Haplom_i with the _Synentognathi_ to form
the order of _Mesichthyes_, or transitional fishes, but the affinities
of either with other groups are quite as well marked as their relation
to each other. Boulenger unites the _Iniomi_ with the _Haplomi_, an
arrangement which apparently has merit, for the most primitive and
non-degenerate _Iniomi_, as _Aulopus_ and _Synodus_, lack both
mesocoracoid and orbitosphenoid. These bones are characteristic of the
_Isospondyli_, but are wanting in _Haplomi_.
There is no adipose dorsal in the typical _Haplomi_, the dorsal is
inserted far back, and the head is generally scaly. Most but not all of
the species are of small size, living in fresh or brackish water, and
they are found in almost all warm regions, though scantily represented
in California, Japan, and Polynesia. The four families of typical
_Haplomi_ differ considerably from one another and are easily
distinguished, although obviously related. Several other families are
provisionally added to this group on account of agreement in technical
characters, but their actual relationships are uncertain.
=The Pikes.=—The _Esocidæ_ have the body long and slender and the mouth
large, its bones armed with very strong, sharp teeth of different sizes,
some of them being movable. The upper jaw is not projectile, and its
margin, as in the _Salmonidæ_, is formed by the maxillary. The scales
are small, and the dorsal fin far back and opposite the anal, and the
stomach is without pyloric cæca. There is but a single genus, _Esox_
(_Lucius_ of Rafinesque), with about five or six living species. Four of
these are North American, the other one being found in Europe, Asia, and
North America.
All the pikes are greedy and voracious fishes, very destructive to other
species which may happen to be their neighbors; "mere machines for the
assimilation of other organisms." Thoreau describes the pike as "the
swiftest, wariest, and most ravenous of fishes, which Josselyn calls the
river-wolf. It is a solemn, stately, ruminant fish, lurking under the
shadow of a lily-pad at noon, with still, circumspect, voracious eye;
motionless as a jewel set in water, or moving slowly along to take up
its position; darting from time to time at such unlucky fish or frog or
insect as comes within its range, and swallowing it at one gulp.
Sometimes a striped snake, bound for greener meadows across the stream,
ends its undulatory progress in the same receptacle."
[Illustration:
FIG. 150.—The Pike, _Esox-lucius_ L. (From life by R. W. Shufeldt.)
]
As food-fishes, all the _Esocidæ_ rank high. Their flesh is white,
fine-grained, disposed in flakes, and of excellent flavor.
The finest of the _Esocidæ_, a species to be compared, as a grand game
fish, with the salmon, is the muskallunge (_Esox masquinongy_).
Technically this species may be known by the fact that its cheeks and
opercles are both naked on the lower half. It may be known also by its
great size and by its color, young and old being spotted with black on a
golden-olive ground.
[Illustration:
FIG. 151.—Muskallunge, _Esox masquinongy_ Mitchill. Ecorse, Mich.
]
The muskallunge is found only in the Great Lake region, where it
inhabits the deeper waters, except for a short time in the spring, when
it enters the streams to spawn. It often reaches a length of six feet
and a weight of sixty to eighty pounds. It is necessarily somewhat rare,
for no small locality would furnish food for more than one such giant.
It is, says Hallock, "a long, slim, strong, and swift fish, in every way
formed for the life it leads, that of a dauntless marauder."
A second species of muskallunge, _Esox ohiensis_, unspotted but vaguely
cross-barred, occurs sparingly in the Ohio River and the upper
Mississippi Valley. It is especially abundant in Chautauqua Lake.
The pike (_Esox lucius_) is smaller than the muskallunge, and is
technically best distinguished by the fact that the opercles are naked
below, while the cheeks are entirely scaly. The spots and cross-bars in
the pike are whitish or yellowish, and always paler than the olive-gray
ground color. It is the most widely distributed of all fresh-water
fishes, being found from the upper Mississippi Valley, the Great Lakes,
and New England to Alaska and throughout northern Asia and Europe. It
reaches a weight of ten to twenty pounds or more, being a large strong
fish in its way, inferior only to the muskallunge. In England _Esox
lucius_ is known as the pike, while its young are called by the
diminutive term pickerel. In America the name pickerel is usually given
to the smaller species, and sometimes even to _Esox lucius_ itself, the
word being with us a synonym for pike, not a diminutive.
Of the small pike or pickerel we have three species in the eastern
United States. They are greenish in color and banded or reticulated,
rather than spotted, and, in all, the opercles as well as the cheeks are
fully covered with scales. One of these (_Esox reticulatus_) is the
common pickerel of the Eastern States, which reaches a respectable size
and is excellent as food. The others, _Esox americanus_ along the
Atlantic seaboard and _Esox vermiculatus_ in the middle West, seldom
exceed a foot in length and are of no economic importance.
Numerous fossil species are found in the Tertiary of Europe, _Esox
lepidotus_ from the Miocene of Baden being one of the earliest and the
best known; in this species the scales are much larger than in the
recent species. The fossil remains would seem to indicate that the
origin of the family was in southern Europe, although most of the living
species are American.
[Illustration:
FIG. 152.—Mud-minnow, _Umbra pygmæa_ (De Kay). New Jersey.
]
=The Mud-minnows.=—Close to the pike is the family of _Umbridæ_, or
mud-minnows, which technically differ from the pikes only in the short
snout, small mouth, and weak dentition. The mud-minnows are small,
sluggish, carnivorous fishes living in the mud at the bottom of cold,
clear streams and ponds. They are extremely tenacious of life, though
soon suffocated in warm waters. The barred mud-minnow of the prairies of
the middle West (_Umbra limi_) often remains in dried sloughs and
bog-holes, and has been sometimes plowed up alive. _Umbra pygmæa_, a
striped species, is found in the Eastern States and _Umbra crameri_ in
bogs and brooks along the Danube. This wide break in distribution seems
to indicate a former wide extension of the range of _Umbridæ_, perhaps
coextensive with _Esox_. Fossil _Umbridæ_ are, however, not yet
recognized.
=The Killifishes.=—Most of the recent _Haplomi_ belong to the family of
_Pœciliidæ_ (killifishes, or Cyprinodonts). In this group the small
mouth is extremely protractile, its margin formed by the premaxillaries
alone much as in the spiny-rayed fishes. The teeth are small and of
various forms according to the food. In most of the herbivorous forms
they are incisor-like, serrate, and loosely inserted in the lips. In the
species that eat insects or worms they are more firmly fixed. The head
is scaly, the stomach without cæca, and the intestines are long in the
plant-eating species and short in the others. There are nearly 200
species, very abundant from New England and California southward to
Argentina, and in Asia and Africa also. In regions where rice is
produced, they swarm in the rice swamps and ditches. Some of them enter
the sea, but none of them go far from shore. Some are brilliantly
colored, and in many species the males are quite unlike the females,
being smaller and more showy. The largest species (_Fundulus_,
_Anableps_) rarely reach the length of a foot, while _Heterandria
formosa_, a diminutive inhabitant of the Florida rivers, scarcely
reaches an inch. Some species are oviparous, but in most of the
herbivorous forms, and some of the others, the eggs are hatched within
the body, and the anal in the male is modified into a long sword-shaped
intromittent organ, placed farther forward than the anal in the female.
The young when born closely resemble the parent. Most of the
insectivorous species swim at the surface, moving slowly with the eyes
partly out of water. This habit in the genus _Anableps_ (four-eyed fish,
or _Cuatro ojos_) is associated with an extraordinary structure of the
eye. This organ is prominent and is divided by a horizontal partition
into two parts, the upper, less convex, adopted for sight in the air,
the lower in the water. The few species of _Anableps_ are found in
tropical America. The species of some genera swim near the bottom, but
always in very shallow waters. All are very tenacious of life, and none
have any commercial value although the flesh is good.
[Illustration:
FIG. 152_a_.—Four-eyed Fish, _Anableps dovii_ Gill. Tehuantepec,
Mexico.
]
The unique structure of the eye of this curious fish has been carefully
studied by Mr. M. C. Marsh, pathologist of the U. S. Fish Commission,
who furnishes the following notes published by Evermann & Goldsborough:
"The eye is crossed by a bar, like the diameter of a circle, and
parallel with the length of the body. This bar is darker than the other
external portions of the eyeball and has its edges darker still.
Dividing the external aspect of the eye equally, it has its lower edge
on the same level as the back of the fish, which is flat and straight
from snout to dorsal, or nearly the whole length of the fish; so that
when the body of the fish is just submerged the level of the water
reaches to this bar, and the lower half of the eye is in water, the
upper half in the air. Upon dissecting the eyeball from the orbit, it
appears nearly round. A membranous sheath covers the external part and
invests most of the ball. It may be peeled off, when the dark bar on the
external portion of the eye is seen to be upon this membrane, which may
correspond to the conjunctiva. The back portion of the eyeball being cut
off, one lens is found. The lining of the ball consists, in front, of
one black layer, evidently choroid. Behind there is a retinal layer. The
choroid layer turns up anteriorly, making a free edge comparable to an
iris. The free edge is chiefly evident in the lower part of the eye. A
large pupil is left, but is divided by two flaps, continuations of the
choroid coat, projecting from either side and overlapping. There are
properly then two pupils, an upper and lower, separated by a band
consisting of the two flaps, which may probably, by moving upward and
downward, increase or diminish the size of either pupil; an upward
motion of the flaps increasing the lower pupil at the expense of the
other, and vice versa."
This division of the pupil into two parts permits the fish, when
swimming at the surface of the water, as is its usual custom, to see in
the air with the upper portion and in the water with the lower. It is
thus able to see not only such insects as are upon the surface of the
water or flying in the air above, but also any that may be swimming
beneath the surface.
[Illustration:
FIG. 153.—Round Minnow, _Cyprinodon variegatus_ Lacépède. St. George
Island, Maryland.
]
According to Mr. E. W. Nelson, "the individuals of this species swim
always at the surface and in little schools arranged in platoons or
abreast. They always swim headed upstream against the current, and feed
upon floating matter which the current brings them. A platoon may be
seen in regular formation breasting the current, either making slight
headway upstream or merely maintaining their station, and on the qui
vive for any suitable food the current may bring. Now and then one may
be seen to dart forward, seize a floating food particle, and then resume
its place in the platoon. And thus they may be observed feeding for long
periods. They are almost invariably found in running water well out in
the stream, or at least where the current is strongest and where
floating matter is most abundant, for it is upon floating matter that
they seem chiefly to depend. They are not known to jump out of the water
to catch insects flying in the air or resting upon vegetation above the
water surface, nor do they seem to feed to any extent upon all small
crustaceans or other portions of the plankton beneath the surface.
[Illustration:
FIG. 154.—Everglade Minnow, _Jordanella floridæ_ Goode & Bean.
Everglades of Florida.
]
"When alarmed—and they are wary and very easily frightened—they escape
by skipping or jumping over the water, 2 or 3 feet at a skip. They rise
entirely out of the water, and at a considerable angle, the head
pointing upward. In descending the tail strikes the water first and
apparently by a sculling motion new impetus is acquired for another
leap. This skipping may continue until the school is widely scattered.
When a school has become scattered, and after the cause of their fright
has disappeared, the individuals soon rejoin each other. First two will
join each other and one by one the others will join them until the whole
school is together again. Rarely do they attempt to dive or get beneath
the surface; when they do they have great difficulty in keeping under
and soon come to the surface again."
[Illustration:
FIG. 155.—Mayfish, _Fundulus majalis_ (L.) (male). Wood's Hole.
]
[Illustration:
FIG. 156.—Mayfish, _Fundulus majalis_ (female). Wood's Hole.
]
[Illustration:
FIG. 157.—Top-minnow, _Zygonectes notatus_ (Rafinesque). Eureka
Springs, Ark.
]
[Illustration:
FIG. 158.—Death Valley Fish, _Empetrichthys merriami_ Gilbert.
Amargosa Desert, Cal. Family _Pœciliidæ_. (After Gilbert.)
]
[Illustration:
FIG. 159.—Sword-tail Minnow, male, _Xiphophorus helleri_ Heckel. The
anal fin modified as an intromittent organ. Vera Cruz.
]
Of the many genera of _Pœciliidæ_, top-minnows, and killifishes we may
mention the following: _Cyprinodon_ is made up of chubby little fishes
of eastern America with tricuspid, incisor teeth, oviparous and
omnivorous. Very similar to these but smaller are the species of
_Lebias_ in southern Europe. _Jordanella floridæ_ of the Florida
everglades is similar, but with the dorsal fin long and its first ray
enlarged and spine-like. It strongly resembles a young sunfish. Most of
the larger forms belong to _Fundulus_, a genus widely distributed from
Maine to Guatemala and north to Kansas and southern California.
_Fundulus majalis_, the Mayfish of the Atlantic Coast, is the largest of
the genus. _Fundulus heteroclitus_, the killifish, the most abundant.
_Fundulus diaphanus_ inhabits sea and lake indiscriminately. _Fundulus
stellifer_ of the Alabama is beautifully colored, as is _Fundulus
zebrinus_ of the Rio Grande. The genus _Zygonectes_ includes dwarf
species similar to _Fundulus_, and _Adinia_ includes those with short,
deep body. _Goodea atripinnis_ with tricuspid teeth lives in warm
springs in Mexico, and several species of _Goodea_, _Gambusia_,
_Pœcilia_, and other genera inhabit hot springs of Mexico, Central
America, and Africa. The genus _Gambusia_, the top-minnows, includes
numerous species with dwarf males having the anal modified. _Gambusia
affinis_ abounds in all kinds of sluggish water in the southern
lowlands, gutters and even sewers included. It brings forth its brood in
early spring. Viviparous and herbivorous with modified anal fin are the
species of _Pœcilia_, abundant throughout Mexico and southward to
Brazil; _Mollienesia_ very similar, with a banner-like dorsal fin,
showily marked, occurs from Louisiana southward, and _Xiphophorus_, with
a sword-shaped lobe on the caudal, abounds in Mexico; _Characodon_ and
_Goodea_ (see Fig. 53, Vol. I) in Mexico have notched teeth, and
finally, _Heterandria_ contains some of the least of fishes, the
handsomely colored males barely half an inch long.
[Illustration:
FIG. 160.—_Goodea luitpoldi_ (Steindachner). A viviparous fish from
Lake Patzcuaro, Mexico. Family _Pœciliidæ_. (After Meek.)
]
In Lake Titicaca in the high Andes is a peculiar genus (_Orestias_)
without ventral fins. Still more peculiar is _Empetrichthys merriami_ of
the desert springs of the hot and rainless Death Valley in California,
similar to _Orestias_, but with enormously enlarged pharyngeals and
pharyngeal teeth, an adaptation to some unknown purpose. Fossil
Cyprinodonts are not rare from the Miocene in southern Europe. The
numerous species are allied to _Lebias_ and _Cyprinodon_, and are
referred to _Prolebias_ and _Pachylebias_. None are American, although
two American extinct genera, _Gephyrura_ and _Proballostomus_, are
probably allied to this group.
=Amblyopsidæ.=—The cavefishes, _Amblyopsidæ_, are the most remarkable of
the haplomous fishes. In this family the vent is placed at the throat.
The form is that of the _Pœciliidæ_, but the mouth is larger and not
protractile. The species are viviparous, the young being born at about
the length of a quarter of an inch.
[Illustration:
FIG. 161.—Dismal Swamp Fish, _Chologaster cornutus_ Agassiz. Supposed
ancestor of _Typhlichthys_. Virginia.
]
In the primitive genus _Chologaster_, the fish of the Dismal Swamp, the
eyes are small but normally developed. _Chologaster cornutus_ abounds in
the black waters of the Dismal Swamp of Virginia, thence southward
through swamps and rice-fields to Okefinokee Swamp in northern Florida.
It is a small fish, less than two inches long, striped with black, and
with the habit of a top-minnow. Other species of _Chologaster_,
possessing eyes and color, but provided also with tactile papillæ, are
found in cave springs in Tennessee and southern Illinois.
[Illustration:
FIG. 162.—Blind Cave-fish, _Typhlichthys subterraneus_ Girard. Mammoth
Cave, Kentucky.
]
From _Chologaster_ is directly descended the small blindfish
_Typhlichthys subterraneus_ of the caves of the Subcarboniferous
limestone rocks of southern Indiana and southward to northern Alabama.
As in _Chologaster_, the ventral fins are wanting. The eyes, present in
the young, become defective and useless in the adult, when they are
almost hidden by other tissues. The different parts of the eye are all
more or less incomplete, being without function. The structure of the
eye has been described in much detail in several papers by Dr. Carl H.
Eigenmann. As to the cause of the loss of eyesight two chief theories
exist—the Lamarckian theory of the inheritance in the species of the
results of disuse in the individual and the Weissmannian doctrine that
the loss of sight is a result of panmixia or cessation of selection.
This may be extended to cover reversal of selection, as in the depths of
the great caves the fish without eyes would be at some slight advantage.
Dr. Eigenmann inclines to the Lamarckian doctrine, but the evidence
brought forward fails to convince the present writer that results of
individual use or disuse ever become hereditary or that they are ever
incorporated in the characters of a species. In the caves of southern
Missouri is an independent case of similar degradation. _Troglichthys
rosæ_, the blindfish of this region, has the eye in a different phase of
degeneration. It is thought to be separately descended from some other
species of _Chologaster_. Of this species Mr. Garman and Mr. Eigenmann
have given detailed accounts from somewhat different points of view.
Concerning the habits of the blindfish (_Troglichthys rosæ_), Mr. Garman
quotes the following from notes of Miss Ruth Hoppin, of Jasper County,
Missouri: "For about two weeks I have been watching a fish taken from a
well. I gave him considerable water, changed once a day, and kept him in
an uninhabited place subject to as few changes of temperature as
possible. He seems perfectly healthy and as lively as when first taken
from the well. If not capable of long fasts, he must live on small
organisms my eye cannot discern. He is hardly ever still, but moves
about the sides of the vessel constantly, down and up, as if needing the
air. He never swims through the body of the water away from the sides
unless disturbed. Passing the finger over the sides of the vessel under
water I find it slippery. I am careful not to disturb this slimy coating
when the water is changed.... Numerous tests convince me that it is
through the sense of touch, and not through hearing, that the fish is
disturbed; I may scream or strike metal bodies together over him as near
as possible, yet he seems to take no notice whatever. If I strike the
vessel so that the water is set in motion, he darts away from that side
through the mass of water, instead of around in his usual way. If I stir
the water or touch the fish, no matter how lightly, his actions are the
same."
[Illustration:
FIG. 163.—Blindfish of the Mammoth Cave, _Amblyopsis spelæus_ (De
Kay). Mammoth Cave, Kentucky.
]
The more famous blindfish of the Mammoth Cave, _Amblyopsis spelæus_,
reaches a length of five inches. It possesses ventral fins. From this
fact we may infer its descent from some extinct genus which, unlike
_Chologaster_, retains these fins. The translucent body, as in the other
blindfishes, is covered with very delicate tactile papillæ, which form a
very delicate organ of touch.
The anomalous position of the vent in _Amblyopsidæ_ occurs again in an
equally singular fish, _Aphredoderus sayanus_, which is found in the
same waters throughout the same region in which _Chologaster_ occurs. It
would seem as if these lowland fishes of the southern swamps were
remains of a once much more extensive fauna.
No fossil allies of _Chologaster_ are known.
=Kneriidæ, etc.=—The members of the order of _Haplomi_, recorded above,
differ widely among themselves in various details of osteology. There
are other families, probably belonging here, which are still more
aberrant. Among these are the _Kneriidæ_, and perhaps the entire series
of forms called _Iniomi_, most of which possess the osteological traits
of the _Haplomi_.
The family of _Kneriidæ_ includes a few very small fishes of the rivers
of Africa.
=The Galaxiidæ.=—The _Galaxiidæ_ are trout-like fishes of the southern
rivers, where they take the place of the trout of the northern zones.
The species lack the adipose fins and have the dorsal inserted well
backward. According to Boulenger these fishes, having no mesocoraoid,
should be placed among the _Haplomi_. Yet their relation to the
_Haplochitonidæ_ is very close and both families may really belong to
the _Isospondyli_. _Galaxias truttaceus_ is the kokopu, or "trout," of
New Zealand. _Galaxias ocellatus_ is the yarra trout of Australia.
Several other species are found in southern Australia, Tasmania,
Patagonia, and the Falkland Islands, and even in South Africa. This very
wide distribution in the rivers remote from each other has given rise to
the suggestion of a former land connection between Australia and
Patagonia. Other similar facts have led some geologists to believe in
the existence of a former great continent called Antarctica, now
submerged except that part which constitutes the present unknown land of
the Antarctic.
As intimated on p. 253, Vol. I, this distribution of _Galaxias_ with
similar anomalies in other groups could not if unsupported by geological
evidence be held to prove the former extension of the Antarctic
continent. Dr. Boulenger[12] has recently shown that _Galaxias_ lives
freely in salt water, a fact sufficient to account for its wide
distribution in the rivers of the southern hemisphere.
Footnote 12:
Dr. Boulenger (_Nature_, Nov. 27, 1902) has the following note on
_Galaxias_: "Most text-books and papers discussing geographical
distribution have made much of the range of a genus of small fishes,
somewhat resembling trout, the _Galaxias_, commonly described as true
fresh-water forms, which have long been known from the extreme south
of South America, New Zealand, Tasmania, and southern Australia. The
discovery, within the last few years, of a species of the same genus
in fresh water near Cape Town, whence it had previously been described
as a loach by F. de Castelnau, has added to the interest, and has been
adduced as a further argument in support of the former existence of an
Antarctic continent. In alluding to this discovery when discussing the
distribution of African fresh-water fishes in the introduction to my
work 'Les Poissons du Bassin du Congo,' in 1901, I observed that,
contrary to the prevailing notion, all species of _Galaxias_ are not
confined to fresh water, and that the fact of some living both in the
sea and in rivers suffices to explain the curious distribution of the
genus; pointing out that in all probability these fishes were formerly
more widely distributed in the seas south of the tropic of Capricorn,
and that certain species, adapting themselves entirely to fresh-water
life, have become localized at the distant points where they are now
known to exist. Although as recently as October last the distinguished
American ichthyologist D. S. Jordan wrote (_Science_, xiv, p. 20): 'We
know nothing of the power of _Galaxias_ to survive submergence in salt
water, if carried in a marine current': it is an established fact,
ascertained some years ago by F. E. Clarke in New Zealand and by R.
Vallentin in the Falkland Islands, that _Galaxias attenuatus_ lives
also in the sea. In New Zealand it periodically descends to the sea,
where it spawns, from January to March, and returns from March to May.
In accordance with these marine habits, this species has a much wider
range than any of the others, being known from Chile, Patagonia,
Tierra del Fuego, the Falkland Islands, New Zealand, Tasmania, and
southern Australia.
"I now wish to draw attention to a communication made by Captain F. W.
Hutton in the last number of the Transactions of the New Zealand
Institute (xxxiv, p. 198), 'On a Marine Galaxias from the Auckland
Islands.' This fish, named _Galaxias bollansi_, was taken out of the
mouth of a specimen of _Merganser australis_ during the collection
excursion to the southern islands of New Zealand made in January,
1901, by His Excellency the Earl of Ranfurly.
"It is hoped that by giving greater publicity to these discoveries the
family _Galaxiidæ_ will no longer be included among those strictly
confined to fresh waters, and that students of the geographical
distribution of animals will be furnished with a clue to a problem
that has so often been discussed on insufficient data. As observed by
Jordan (_l. c._), all anomalies in distribution cease to be such when
the facts necessary to understand them are at hand.'
"Of the fresh-water species of _Galaxias_, eight are known from New
Zealand and the neighboring islands, seven from New South Wales, three
or four from south Australia, one from west Australia, two from
Tasmania, seven from South America, from Chile southwards, and one
from the Cape of Good Hope."
_Neochanna_ is an ally of _Galaxias_ living in burrows in the clay or
mud like a crayfish, often at a distance from water. As in various other
mud-living types, the ventral fins are obsolete.
=Order Xenomi.=—We must place near the _Haplomi_ the singular group of
_Xenomi_ (ξενός, strange; ὤμος, shoulder), regarded by Dr. Gill as a
distinct order. Externally these fish much resemble the mud-minnows,
differing mainly in the very broad pectorals. But the skeleton is thin
and papery, the two coracoids forming a single cartilaginous plate
imperfectly divided. The pectorals are attached directly to this without
the intervention of actinosts, but in the distal third, according to Dr.
Charles H. Gilbert, the coracoid plate begins to break up into a fringe
of narrow cartilaginous strips. These about equal the very large number
(33 to 36) of pectoral rays, the basal part of each ray being slightly
forked to receive the tip of the cartilaginous strip.
[Illustration:
FIG. 164.—Alaska Blackfish, _Dallia pectoralis_ (Bean). St. Michaels,
Alaska.
]
"In the deep-sea eels of the order _Heteromi_ there is a somewhat
similar condition of the coracoid elements inasmuch as the hypercoracoid
and hypocoracoid though present are merely membranous elements
surrounded by cartilage and the actinosts are greatly reduced. It seems
probable that we are dealing in the two cases with independent
degeneration of the shoulder-girdle and that the two groups (_Xenomi_
and _Heteromi_) are not really related." (Gilbert.)
Of the single family _Dalliidæ_, one species is known, the Alaska
blackfish, _Dallia pectoralis_.
This animal, formed like a mud-minnow, reaches a length of eight inches
and swarms in the bogs and sphagnum swamps of northwestern Alaska and
westward through Siberia. It is found in countless numbers according to
its discoverer, Mr. L. M. Turner, "wherever there is water enough to wet
the skin of a fish," and wherever it occurs it forms the chief food of
the natives. Its vitality is most extraordinary. Blackfishes will remain
frozen in baskets for weeks and when thawed out are as lively as ever.
Turner gives an account of a frozen individual swallowed by a dog which
escaped in safety after being thawed out by the heat of the dog's
stomach.