Chapter XXI: The Fishes of the Deep Sea (9)

Plagyodus.--Body elongate, compressed, scaleless; snout much
produced, with very wide cleft of the mouth. Intermaxillary very
long and slender; maxillary thin, immovable. Teeth in the jaws
and of the palate very unequal in size, the majority pointed
and sharp, some very large and lanceolate. Eye large. Pectoral
and ventral fins well developed; the rayed dorsal fin occupies
the whole length of the back from the occiput to opposite the
anal fin; adipose and anal fins of moderate size. Caudal forked.
Branchiostegals six or seven.

This is one of the largest and most formidable deep-sea fishes. One species only is well known, _P. ferox_, from Madeira and the sea off Tasmania; other species have been noticed from Cuba and the North Pacific, but it is not evident in what respects they differ specifically from _P. ferox_. This fish grows to a length of six feet, and from the stomach of one example have been taken several Octopods, Crustaceans, Ascidians, a young Brama, twelve young Boar-fishes, a Horse-mackerel, and one young of its own species. The stomach is coecal; the commencement of the intestine has extremely thick walls, its inner surface being cellular, like the lung of a reptile; a pyloric appendage is absent. All the bones are extremely thin, light, and flexible, containing very little earthy matter; singular is the development of a system of abdominal ribs, symmetrically arranged on both sides, and extending the whole length of the abdomen. Perfect specimens are rarely obtained on account of the want of coherence of the muscular and osseous parts, caused by the diminution of pressure when the fish reaches the surface of the water. The exact depth at which _Plagyodus_ lives is not known; probably it never rises above a depth of 300 fathoms.

The other less important genera belonging to this family are _Aulopus_, _Chlorophthalmus_, _Scopelosaurus_, _Odontostomus_, and _Nannobrachium_.

THIRD FAMILY--CYPRINIDÆ.

_Body generally covered with scales; head naked. Margin of the upper jaw formed by the intermaxillaries. Belly rounded, or, if trenchant, without ossifications. No adipose fin. Stomach without blind sac. Pyloric appendages none. Mouth toothless; lower pharyngeal bones well developed, falciform, sub-parallel to the branchial arches, provided with teeth, which are arranged in one, two, or three series. Air-bladder large, divided into an anterior and posterior portion by a constriction, or into a right or left portion, enclosed in an osseous capsule. Ovarian sacs closed._

The family of “Carps” is the one most numerously represented in the fresh waters of the Old World and of North America. Also numerous fossil remains are found in tertiary freshwater-formations, as in the limestones of Oeningen and Steinheim, in the lignites of Bonn, Stöchen, Bilin, and Ménat, in the marl slates and carbonaceous shales of Licata in Sicily, and of Padang in Sumatra, in corresponding deposits of Idaho in North America. The majority can be referred to existing genera: _Barbus_, _Thynnichthys_, _Gobio_, _Leuciscus_, _Tinca_, _Amblypharyngodon_, _Rhodeus_, _Cobitis_, _Acanthopsis_, only a few showing characters different from those of living genera: _Cyclurus_, _Hexapsephus_, _Mylocyprinus_ (tertiary of North America).

Most Carps feed on vegetable and animal substances; a few only are exclusive vegetable feeders. There is much less diversity of form and habits in this family than in the Siluroids; however, the genera are sufficiently numerous to demand a further subdivision of the family into groups.

I. CATOSTOMINA.--_Pharyngeal teeth in a single series, exceedingly numerous and closely set. Dorsal fin elongate, opposite to the ventrals; anal short, or of moderate length. Barbels none._

These fishes are abundant in the lakes and rivers of North America, more than thirty species having been described, and many more named, by American ichthyologists. Two species are known from North-Eastern Asia. They are generally called “Suckers,” but their vernacular nomenclature is very arbitrary and confused. Some of the species which inhabit the large rivers and lakes grow to a length of three feet and a weight of fifteen pounds. The following genera may be distinguished:--_Catostomus_, “Suckers,” “Red-horses,” “Stone-rollers,” “White Mullets;” _Moxostoma_; _Sclerognathus_, “Buffaloes,” “Black Horses;” and _Carpiodes_, “Spear-fish,” “Sail-fish.”

II. CYPRININA.--_Anal fin very short, with not more than five or six, exceptionally seven, branched rays. Dorsal fin opposite ventrals. Abdomen not compressed. Lateral line running along the median line of the tail. Mouth frequently with barbels, never more than four in number. Pharyngeal teeth generally in a triple series in the Old World genera; in a double or single series in the North American forms, which are small and feebly developed. Air-bladder present, without osseous covering._

CYPRINUS.--Scales large. Dorsal fin long, with a more or less
strong serrated osseous ray; anal short. Snout rounded, obtuse,
mouth anterior, rather narrow. Pharyngeal teeth, 3. 1. 1.-1. 1.
3, molar-like. Barbels four.

The “Carp” (_C. carpio_, “Karpfen,” “La carpe,”) is originally a native of the East, and abounds in a wild state in China, where it has been domesticated for many centuries; thence it was transported to Germany and Sweden, and the year 1614 is assigned as the date of its first introduction into England. It delights in tranquil waters, preferring such as have a muddy bottom, and the surface partially shaded with plants. Its food consists of the larvæ of aquatic insects, minute testacea, worms, and the tender blades and shoots of plants. The leaves of lettuce, and other succulent plants of a similar kind, are said to be particularly agreeable to them, and to fatten them sooner than any other food. Although the Carp eats with great voracity when its supply of aliment is abundant, it can subsist for an astonishing length of time without nourishment. In the winter, when the Carps assemble in great numbers, and bury themselves among the mud and the roots of plants, they often remain for many months without eating. They can also be preserved alive for a considerable length of time out of the water, especially if care be taken to moisten them occasionally as they become dry. Advantage is often taken of this circumstance to transport them alive, by packing them among damp herbage or damp linen; and the operation is said to be unattended with any risk to the animal, especially if the precaution be taken to put a piece of bread in its mouth steeped in brandy!

The fecundity of these fishes is very great, and their numbers consequently would soon become excessive but for the many enemies by which their spawn is destroyed. No fewer than 700,000 eggs have been found in the ovaries of a single Carp, and that, too, by no means an individual of the largest size. Their growth is very rapid, more so perhaps than that of any other Freshwater fish, and the size which they sometimes attain is very considerable. In certain lakes in Germany individuals are occasionally taken weighing thirty or forty pounds; and Pallas relates that they occur in the Volga five feet in length, and even of greater weight than the examples just alluded to. The largest of which we have any account is that mentioned by Bloch, taken near Frankfort-on-the-Oder, which weighed seventy pounds, and measured nearly nine feet in length,--a statement the accuracy of which is very much open to doubt.

Like other domesticated animals the Carp is subject to variation; some individuals, especially when they have been bred under unfavourable circumstances, have a lean and low body; others are shorter and higher. Some have lost every trace of scales, and are called “Leather-carps;” others retain them along the lateral line and on the back only (“Spiegelkarpfen” of the Germans). Finally, in some are the fins much prolonged, as in certain varieties of the Gold-fish. Cross-breeds between the Carp and the Crucian Carp are of common occurrence. The Carp is much more esteemed as food in inland countries than in countries where the more delicate kinds of sea fishes can be obtained.

CARASSIUS differs from _Cyprinus_ in lacking barbels; its
pharyngeal teeth are compressed, in a single series, 4–4.

Two well-known species belong to this genus. The “Crucian Carp” (_C. carassius_, “Karausche”) is generally distributed over Central and Northern Europe, and extends into Italy and Siberia. It inhabits stagnant waters only, and is so tenacious of life that it will survive a lengthened sojourn in the smallest pools, where, however, it remains stunted; whilst in favourable localities it attains to a length of twelve inches. It is much subject to variation of form; very lean examples are commonly called “Prussian Carps.” Its usefulness consists in keeping ponds clean from a super-abundance of vegetable growth, and in serving as food for other more esteemed fishes. The second species is the “Gold-fish,” _Carassius auratus_. It is of very common occurrence in a wild state in China and the warmer parts of Japan, being entirely similar in colour to the Crucian Carp. In a domesticated state it loses the black or brown chromatophors, and becomes of a golden-yellow colour; perfect Albinos are comparatively scarcer. Many varieties and monstrosities have been produced during the long period of its domestication; the variety most highly priced at present being the so-called “Telescope-fish,” of which a figure is annexed. The Gold-fish is said to have been first brought to England in the year 1691, and is now distributed over nearly all the civilised parts of the world.

CATLA.--Scales of moderate size. Dorsal fin without osseous ray,
with more than nine branched rays, commencing nearly opposite to
the ventrals. Snout broad, with the integuments very thin; there
is no upper lip, the lower with a free continuous posterior
margin. Symphysis of the mandibulary bones loose, with prominent
tubercles. Mouth anterior. Barbels none. Gill-rakers very long,
fine, and closely set. Pharyngeal teeth, 5. 3. 2.-2. 3. 5.

The “Catla” (_C. buchanani_), one of the largest Carps of the Ganges, growing to a length of more than three feet, and esteemed as food.

LABEO.--Scales of moderate or small size. Dorsal fin without
osseous ray, with more than nine branched rays, commencing
somewhat in advance of the ventrals. Snout obtusely rounded,
the skin of the maxillary region being more or less thickened,
forming a projection beyond the mouth. Mouth transverse,
inferior, with the lips thickened, each or one of them being
provided with an inner transverse fold, which is covered with a
deciduous horny substance forming a sharp edge, which, however,
does not rest upon the bone as base, but is soft and movable.
Barbels very small, two or four; the maxillary barbels more or
less hidden in a groove behind the angle of the mouth. Anal
scales not enlarged. Pharyngeal teeth uncinate, 5. 4. 2.-2. 4.
5. Snout generally more or less covered with hollow tubercles.

About thirteen species are known from rivers of tropical Africa and the East Indies.

DISCOGNATHUS.--Scales of moderate size. Dorsal fin without
osseous ray, with not more than nine branched rays, commencing
somewhat in advance of the ventrals. Snout obtusely rounded,
more or less depressed, projecting beyond the mouth, more or
less tubercular. Mouth inferior, transverse, crescent-shaped;
lips broad, continuous, with an inner sharp edge of the jaws,
covered with horny substance on the lower jaw; upper lip more
or less distinctly fringed; lower lip modified into a suctorial
disk, with free anterior and posterior margins. Barbels two or
four; if two, the upper are absent. Anal scales not enlarged.
Pectoral fins horizontal. Pharyngeal teeth, 5. 4. 2.-2. 4. 5.

A small fish (_D. lamta_), extremely abundant in almost all the mountain streams from Abyssinia and Syria to Assam.

CAPOËTA.--Scales small, of moderate or large size. Dorsal fin
with or without a strong osseous ray, with not more than nine
branched rays. Snout rounded, with the mouth transverse and at
its lower side; each mandible angularly bent inwards in front,
the anterior mandibular edge being nearly straight, sharpish,
and covered with a horny brown layer. No lower labial fold.
Barbels two (rarely four), or entirely absent. Anal scales not
conspicuously enlarged. Pharyngeal teeth compressed, truncated,
5 or 4. 3. 2–2. 3. 4 or 5.

Characteristic of the fauna of Western Asia; one species from Abyssinia. Of the fifteen species known _C. damascina_ deserves to be specially mentioned, being abundant in the Jordan and other rivers of Syria and Asia Minor.

BARBUS.--Scales of small, moderate, or large size. Dorsal
fin generally with the (third) longest simple ray ossified,
enlarged, and frequently serrated; never, or only exceptionally,
with more than nine branched rays, commencing opposite or nearly
opposite to the root of the ventral fin. Eyes without adipose
eyelid. Anal fin frequently very high. Mouth arched, without
inner folds, inferior or anterior; lips without horny covering.
Barbels short, four, two, or none. Anal scales not enlarged.
Pharyngeal teeth 5. 4 or 3. 3 or 2.-2 or 3. 3 or 4. 5. Snout but
rarely with tubercles or pore-like grooves.

No other genus of Cyprinoids is composed of so many species as the genus of “Barbels,” about 200 being known from the tropical and temperate parts of the Old World; it is not represented in the New World. Although the species differ much from each other in the form of the body, number of barbels, size of the scales, strength of the first dorsal ray or spine, etc., the transition between the extreme forms is so perfect that no further generic subdivision should be attempted. Some attain a length of six feet, whilst others never exceed a length of two inches. The most noteworthy are the large Barbels of the Tigris (_B. subquincunciatus_, _B. esocinus_, _B. scheich_, _B. sharpeyi_); the common Barbel of Central Europe and Great Britain (_B. vulgaris_); the “Bynni” of the Nile (_B. bynni_); _B. canis_ from the Jordan; the “Mahaseer” of the mountain streams of India (_B. mosal_), probably the largest of all species, the scales of which are sometimes as large as the palm of a hand. The small, large-scaled species are especially numerous in the East Indies and the fresh waters of Tropical Africa.

THYNNICHTHYS.--Scales small. Dorsal fin without an osseous
ray, with not more than nine branched rays, commencing nearly
opposite the ventrals. Head large, strongly compressed; eye
without well-developed adipose membrane, in the middle of
the depth of the head. Snout with the integuments very thin;
there is no upper lip, and the lower jaw has a thin labial
fold on the sides only. Mouth anterior and lateral; barbels
none. Gill-rakers none; laminæ branchiales long, half as long
as the post-orbital portion of the head; pseudobranchiæ none.
Pharyngeal teeth lamelliform, with flat oblong crown, 5. 3 or 4.
2–2. 4 or 3. 5, the teeth of the three series being wedged into
one another.

Three species from the East Indies.

OREINUS.--Scales very small. Dorsal fin with a strong osseous
serrated ray, opposite to the ventrals. Snout rounded, with the
mouth transverse, and at its lower side; mandibles broad, short,
and flat, loosely joined together; margin of the jaw covered
with a thick horny layer; a broad fringe-like lower lip, with
free posterior margin. Barbels four. Vent and anal fin in a
sheath, covered with enlarged tiled scales. Pharyngeal teeth
pointed, more or less hooked, 5. 3. 2–2. 3. 5.

Three species from mountain streams of the Himalayas.

SCHIZOTHORAX.--Hill-barbels, with the same singular sheath on
each side of the vent, as in the preceding genus; but they
differ in having the mouth normally formed, with mandibles of
the usual length and width.

Seventeen species are known from fresh waters of the Himalayas, and north of them. Other genera from the same region, and with the anal sheath, are _Ptychobarbus_, _Gymnocypris_, _Schizopygopsis_, and _Diptychus_.

GOBIO.--Scales of moderate size; lateral line present. Dorsal
fin short, without spine. Mouth inferior; mandible not
projecting beyond the upper jaw when the mouth is open; both
jaws with simple lips; a small but very distinct barbel at the
angle of the mouth, quite at the extremity of the maxillary.
Gill-rakers very short; pseudobranchiæ. Pharyngeal teeth, 5. 3
or 2.--2 or 3. 5, hooked at the end.

The “Gudgeons” are small fishes of clear fresh waters of Europe; they are, like the barbels, animal feeders. In Eastern Asia they are represented by two closely allied genera, _Ladislavia_ and _Pseudogobio_.

CERATICHTHYS.--Scales of moderate or small size; lateral line
present. Dorsal fin short, without spine, not or but slightly
in advance of the ventrals. Mouth subinferior; the lower jaw
does not project beyond the upper when the mouth is open;
intermaxillaries protractile from below the maxillaries; both
jaws with thickish lips; a small barbel at the angle of the
mouth, quite at the extremity of the maxillary. Gill-rakers very
short and few in number: pseudobranchiæ. Pharyngeal teeth 4–4.
hooked at the end (sometimes 4, 1--1. 4).

About ten species are known from North America; they are small, and called “Chub” in the United States. _C. biguttatus_ is, perhaps, the most widely-diffused Freshwater-fish in the United States, and common everywhere. Breeding males have generally a red spot on each side of the head.

Other similar genera from the fresh waters of North America, and generally called “Minnows,” are _Pimephales_ (the “Black Head”), _Hyborhynchus_, _Hybognathus_, _Campostoma_ (the “Stone-lugger”), _Ericymba_, _Cochlognathus_, _Exoglossum_ (the “Stone Toter” or “Cut-lips”), and _Rhinichthys_ (the “Long-nosed Dace”).

The remaining Old World genera belonging to the group _Cyprinina_ are _Cirrhina_, _Dangila_, _Osteochilus_, _Barynotus_, _Tylognathus_, _Abrostomus_, _Crossochilus_, _Epalzeorhynchus_, _Barbichthys_, _Amblyrhynchichthys_, _Albulichthys_, _Aulopyge_, _Bungia_, and _Pseudorasbora_.

III. ROHTEICHTHYINA.--_Anal fin very short, with not more than six branched rays. Dorsal fin behind ventrals. Abdomen compressed. Lateral line running along the median line of the tail. Mouth without barbels. Pharyngeal teeth in a triple series._

One genus and species only, _Rohteichthys microlepis_, from Borneo and Sumatra.

IV. LEPTOBARBINA.--_Anal fin very short, with not more than six branched rays. Dorsal fin opposite to ventrals. Abdomen not compressed. Lateral line running in the lower half of the tail. Barbels present, not more than four in number. Pharyngeal teeth in a triple series._

One genus and species only, _Leptobarbus hoevenii_, from Borneo and Sumatra.

V. RASBORINA.--_Anal fin very short, with not more than six branched rays. Dorsal fin inserted behind the origin of the ventrals. Abdomen not compressed. Lateral line running along the lower half of the tail, if complete. Mouth sometimes with barbels, which are nevermore than four in number. Pharyngeal teeth in a triple, or single series. Air-bladder present, without osseous covering._

RASBORA.--Scales large, or of moderate size, there being
generally four and a half longitudinal series of scales between
the origin of the dorsal fin and the lateral line, and one
between the lateral line and the ventral. Lateral line curved
downwards. Dorsal fin with seven or eight branched rays, not
extending to above the anal, which is seven-rayed. Mouth of
moderate width, extending to the front margin of the orbit,
with the lower jaw slightly prominent, and provided with three
prominences in front, fitting into grooves of the upper jaw;
barbels none, in one species two. Gill-rakers short, lanceolate.
Pseudobranchiæ. Pharyngeal teeth in three series, uncinate.

Thirteen species of small size from the East Indian Continent and Archipelago, and from rivers on the east coast of Africa.

AMBLYPHARYNGODON.--Scales small; lateral line incomplete. Dorsal
fin without an osseous ray, with not more than nine branched
rays, commencing a little behind the origin of the ventrals.
Head of moderate size, strongly compressed; eye without adipose
membrane; snout with the integuments very thin; there is no
upper lip, and the lower jaw has a short labial fold on the
sides only. Mouth anterior, somewhat directed upwards, with
the lower jaw prominent. Barbels none. Gill-rakers extremely
short; pseudobranchiæ. Pharyngeal teeth molar-like, with their
crowns concave, 3. 2. 1.--1. 2. 3. Intestinal tract narrow, with
numerous convolutions.

Three species of small size from the Continent of India.

To the same group belong _Luciosoma_, _Nuria_, and _Aphyocypris_, from the same geographical region.

VI. SEMIPLOTINA.--_Anal fin short, with seven branched rays, not extending forwards to below the dorsal. Dorsal fin elongate, with an osseous ray. Lateral line running along the middle of the tail. Mouth sometimes with barbels._

Two genera: _Cyprinion_, from Syria and Persia, and _Semiplotus_ from Assam.

VII. XENOCYPRIDINA.--_Anal fin rather short, with seven or more branched rays, not extending forwards to below the dorsal fin. Dorsal short, with an osseous ray. Lateral line running along the middle of the tail. Mouth sometimes with barbels. Pharyngeal teeth in a triple or double series._

Three genera: _Xenocypris_ and _Paracanthobrama_ from China; and _Mystacoleucus_ from Sumatra.

VIII. LEUCISCINA.--_Anal fin short or of moderate length, with from eight to eleven branched rays, not extending forwards to below the dorsal. Dorsal fin short, without osseous ray. Lateral line, if complete, running along, or nearly in, the middle of the tail. Mouth generally without barbels. Pharyngeal teeth in a single or double series._

LEUCISCUS.--Body covered with imbricate scales. Dorsal fin
commencing opposite, rarely behind, the ventrals. Anal fin
generally with from nine to eleven, rarely with eight (in small
species only), and still more rarely with fourteen rays. Mouth
without structural peculiarities; lower jaw not trenchant;
barbels none. Pseudobranchiæ. Pharyngeal teeth conical or
compressed, in a single or double series. Intestinal tract
short, with only a few convolutions.

The numerous species of this genus are comprised under the name of “White-fish;” they are equally abundant in the northern temperate zone of both hemispheres, about forty species being known from the Old World, and about fifty from the New. The most noteworthy species of the former Fauna are the “Roach” (_L. rutilus_, see Fig. 21, p. 50), common all over Europe north of the Alps; the “Chub” (_L. cephalus_), extending into Northern Italy and Asia Minor; the “Dace” (_L. leuciscus_), a companion of the Roach; the “Id” or “Nerfling” (_L. idus_), from the central and northern parts of Continental Europe, domesticated in some localities of Germany, in this condition assuming the golden hue of semi-albinism, like a Gold-fish, and then called the “Orfe;” the “Rudd,” or “Red-eye” (_L. erythrophthalmus_), distributed all over Europe and Asia Minor, and distinguished by its scarlet lower fins; the “Minnow” (_L. phoxinus_), abundant everywhere in Europe, and growing to a length of seven inches in favourable localities. The North American species are much less perfectly known; the smaller ones are termed “Minnows,” the larger “Shiner” or “Dace.” The most common are _L. cornutus_ (Red-fin, Red Dace); _L. neogæus_, a minnow resembling the European species, but with incomplete lateral line; _L. hudsonius_, the “Spawn-eater” or “Smelt.”

TINCA.--Scales small, deeply embedded in the thick skin; lateral
line complete. Dorsal fin short, its origin being opposite the
ventral fin; anal short; caudal subtruncated. Mouth anterior;
jaws with the lips moderately developed; a barbel at the angle
of the mouth. Gill-rakers short, lanceolate; pseudobranchiæ
rudimentary. Pharyngeal teeth 4 or 5.-5, cuneiform, slightly
hooked at the end.

Only one species of “Tench” is known (_T. tinca_), found all over Europe in stagnant waters with soft bottom. The “Golden Tench” is only a variety of colour, an incipient albinism like the Gold-fish and Id. Like most other Carps of this group it passes the winter in a state of torpidity, during which it ceases to feed. It is extremely prolific, 297,000 ova having been counted in one female; its spawn is of a greenish colour.

LEUCOSOMUS.--Scales of moderate or small size; lateral line
present. Dorsal fin commencing opposite, or nearly opposite, to
the ventral. Anal fin short. Mouth anterior or sub-anterior;
intermaxillaries protractile. A very small barbel at the
extremity of the maxillary. Lower jaw with rounded margin, and
with the labial folds well developed laterally. Gill-rakers
short; pseudobranchiæ. Pharyngeal teeth in a double series.

A North American genus, to which belong some of the most common species of the United States. _L. pulchellus_ (the “Fall-fish,” “Dace,” or “Roach”), one of the largest White-fishes of the Eastern States, attaining to a length of 18 inches, and abundant in the rapids of the larger rivers. _L. corporalis_ (the “Chub”), common everywhere from New England to the Missouri region.

CHONDROSTOMA.--Scales of moderate size or small. Lateral line
terminating in the median line of the depth of the tail. Dorsal
fin with not more than nine branched rays, inserted above the
root of the ventrals. Anal fin rather elongate, with ten or more
rays. Mouth inferior, transverse, lower jaw with a cutting edge,
covered with a brown horny layer. Barbels none. Gill-rakers
short, fine; pseudobranchiæ. Pharyngeal teeth 5 or 6 or 7.-7 or
6 or 5, knife-shaped, not denticulated. Peritoneum black.

Seven species from the Continent of Europe and Western Asia.

Other Old World genera belonging to the _Leuciscina_ are _Myloleucus_, _Ctenopharyngodon_, and _Paraphoxinus_; from North America: _Mylopharodon_, _Meda_, _Orthodon_, and _Acrochilus_.

IX. RHODEINA.--_Anal fin of moderate length, with from nine to twelve branched rays, extending forwards to below the dorsal. Dorsal fin short, or of moderate length. Lateral line, if complete, running along or nearly in the middle of the tail. Mouth with very small, or without any barbels. Pharyngeal teeth in a single series._

Very small roach-like fishes inhabiting chiefly Eastern Asia and Japan, one species (_Rh. amarus_) advancing into Central Europe. The thirteen species known have been distributed among four genera, _Achilognathus_, _Acanthorhodeus_, _Rhodeus_, and _Pseudoperilampus_. In the females a long external urogenital tube is developed annually during the spawning season. The European species is known in Germany by the name of “Bitterling.”

X. DANIONINA.--_Anal fin of moderate length or elongate, with not less, and generally more, than eight branched rays. Lateral line running along the lower half of the tail. Mouth with small, or without any, barbels. Abdomen not trenchant. Pharyngeal teeth in a triple or double series._

Small fishes from the East Indian Continent, Ceylon, the East Asiatic Islands, and a few from East African Rivers, The genera belonging to this group are _Danio_, _Pteropsarion_, _Aspidoparia_, _Barilius_, _Bola_, _Scharca_, _Opsariichthys_, _Squaliobarbus_, and _Ochetobus_: altogether about forty species.

XI. HYPOPHTHALMICHTHYINA.--_Anal fin elongate. Lateral line running nearly along the median line of the tail. Mouth without barbels. Abdomen not trenchant. No dorsal spine. Pharyngeal teeth in a single series._

One genus (_Hypophthalmichthys_) with two species from China.

XII. ABRAMIDINA.--_Anal fin elongate. Abdomen, or part of the abdomen, compressed._

ABRAMIS.--Body much compressed, elevated, or oblong. Scales
of moderate size. Lateral line present, running in the lower
half of the tail. Dorsal fin short, with spine, opposite to the
space between ventrals and anals. Lower jaw generally shorter,
and rarely longer than the upper. Both jaws with simple lips,
the lower labial fold being interrupted at the symphysis of
the mandible. Upper jaw protractile. Gill-rakers rather short;
pseudobranchiæ. The attachment of the branchial membrane to the
isthmus takes place at some distance behind the vertical from
the orbit. Pharyngeal teeth in one or two series, with a notch
near the extremity. Belly behind the ventrals compressed into an
edge, the scales not extending across it.

The “Breams” are represented in the temperate parts of both northern hemispheres; in Europe there occur the “Common Bream,” _A. brama_; the “Zope,” _A. ballerus_; _A. sapa_; the “Zärthe,” _A. vimba_; _A. elongatus_; the “White Bream,” _A. blicca_; _A. bipunctatus_. Of these _A. brama_ and _A. blicca_ are British; the former being one of the most common fishes, and sometimes attaining to a length of two feet. Crosses between these two species, and even with other Cyprinoids, are not rare. Of the American species _A. americanus_ (“Shiner,” “Bream”) is common and widely distributed; like the European Bream it lives chiefly in stagnant waters or streams with a slow current.

ASPIUS.--Body oblong; scales of moderate size; lateral line
complete, terminating nearly in the middle of the depth of the
tail. Dorsal fin short, without spine, opposite to the space
between the ventrals and anal; anal fin elongate, with thirteen
or more rays. Lower jaw more or less conspicuously projecting
beyond the upper. Lips thin, simple, the lower labial fold being
at the symphysis; upper jaw but little protractile. Gill-rakers
short and widely set; pseudobranchiæ. The attachment of the
branchial membrane to the isthmus takes place below the hind
margin of the orbit. Pharyngeal teeth hooked, 5. 3.-3 or 2. 5 or
4. Belly behind the ventrals compressed, the scales covering the
edge.

Four species from Eastern Europe to China.

ALBURNUS.--Body more or less elongate; scales of moderate size;
lateral line present, running below the median line of the
tail. Dorsal fin short, without spine, opposite to the space
between ventrals and anal; anal fin elongate, with more than
thirteen rays. Lower jaw more or less conspicuously projecting
beyond the upper. Lips thin, simple, the lower labial fold
being interrupted at the symphysis of the mandible. Upper jaw
protractile. Gill-rakers slender, lanceolate, closely set;
pseudobranchiæ. The attachment of the branchial membrane to
the isthmus takes place below the hind margin of the orbit.
Pharyngeal teeth in two series, hooked. Belly behind the
ventrals compressed into an edge, the scales not extending
across it.

“Bleak” are numerous in Europe and Western Asia, fifteen species being known. The common Bleak (_A. alburnus_) is found north of the Alps only, and represented by another species (_A. alburnellus_, “Alborella,” or “Avola”) in Italy.

Of the other genera referred to this group, _Leucaspius_ and _Pelecus_ belong to the European Fauna; _Pelotrophus_ is East African; all the others occur in the East Indies or the temperate parts of Asia, viz. _Rasborichthys_, _Elopichthys_, _Acanthobrama_ (Western Asia), _Osteobrama_, _Chanodichthys_, _Hemiculter_, _Smiliogaster_, _Toxabramis_, _Culter_, _Eustira_, _Chela_, _Pseudolabuca_, and _Cachius_.

XIII. HOMALOPTERINA.--_Dorsal and anal fins short, the former opposite to ventrals. Pectoral and ventral fins horizontal, the former with the outer rays simple. Barbels six or none. Air-bladder absent. Pharyngeal teeth in a single series, from ten to sixteen in number._

Inhabitants of hill-streams in the East Indies; they are of small size and abundant where they occur. Thirteen species are known belonging to the genera _Homaloptera_, _Gastromyzon_, _Crossostoma_, and _Psilorhynchus_.

XIV. COBITIDINA.--_Mouth surrounded by six or more barbels. Dorsal fin short or of moderate length; anal fin short. Scales small, rudimentary, or entirely absent. Pharyngeal teeth in a single series, in moderate number. Air-bladder partly or entirely enclosed in a bony capsule. Pseudobranchiæ none_: Loaches.

MISGURNUS.--Body elongate, compressed. No sub-orbital spine. Ten
or twelve barbels, four belonging to the mandible. Dorsal fin
opposite to the ventrals; caudal rounded.

Four species from Europe and Asia. _M. fossilis_ is the largest of European Loaches, growing to a length of ten inches; it occurs in stagnant waters of eastern and southern Germany and northern Asia. In China and Japan it is replaced by an equally large species, _M. anguillicaudatus_.

NEMACHILUS.--No erectile sub-orbital spine. Six barbels, none at
the mandible. Dorsal fin opposite to the ventrals.

The greater number of Loaches belong to this genus; about fifty species are known from Europe and temperate Asia; such species as extend into tropical parts inhabit streams of high altitudes. Loaches are partial to fast-running streams with stony bottom, and exclusively animal feeders. In spite of their small size they are esteemed as food where they occur in sufficient abundance. The British species, _N. barbatulus_, is found all over Europe except Denmark and Scandinavia.

COBITIS.--Body more or less compressed, elongate; back not
arched. A small, erectile, bifid sub-orbital spine below the
eye. Six barbels only on the upper jaw. Dorsal fin inserted
opposite to ventrals. Caudal rounded or truncate.

Only three species are known, of which _C. tænia_ occurs in Europe. It is scarce and very local in Great Britain.

BOTIA.--Body compressed, oblong; back more or less arched. Eyes
with a free circular eyelid; an erectile bifid sub-orbital
spine. Six barbels on the upper jaw, sometimes two others at the
mandibulary symphysis. Dorsal fin commencing in advance of the
root of the ventrals; caudal fin forked. Air-bladder consisting
of two divisions: the anterior enclosed in a partly osseous
capsule, the posterior free, floating in the abdominal cavity.

This genus is more tropical than any of the preceding, and the majority of the species (eight in number) are finely coloured. The more elevated form of their body, and the imperfect ossification of the capsules of the air-bladder, the divisions of which are not side by side, but placed in the longitudinal axis of the body, indicate likewise that this genus is more adapted for still waters of the plains than for the currents of hill-streams.

Other genera from tropical India are _Lepidocephalichthys_, _Acanthopsis_, _Oreonectes_ (hills near Hong-Kong), _Paramisgurnus_ (Yan-tse-Kiang), _Lepidocephalus_, _Acanthophthalmus_, and _Apua_.

FOURTH FAMILY--KNERIIDÆ.

_Body scaly, head naked. Margin of the upper jaw formed by the intermaxillaries. Dorsal and anal fins short, the former belonging to the abdominal portion of the vertebral column. Teeth none, either in the mouth or pharynx. Barbels none. Stomach siphonal; no pyloric appendages. Pseudobranchiæ none. Branchiostegals three; air-bladder long, not divided. Ovaries closed._

Small loach-like fishes from fresh waters of tropical Africa; two species only, _Kneria angolensis_ and _K. spekii_, are known.

FIFTH FAMILY--CHARACINIDÆ.

_Body covered with scales, head naked; barbels none. Margin of the upper jaw formed by the intermaxillaries in the middle and by the maxillaries laterally. Generally a small adipose fin behind the dorsal. Pyloric appendages more or less numerous; air-bladder transversely divided into two portions, and communicating with the organ of hearing by means of the auditory ossicles. Pseudobranchiæ none._

The fishes of this family are confined to the fresh waters of Africa, and especially of tropical America, where they replace the Cyprinoids, with which family, however, they have but little in common as far as their structural characteristics are concerned. Their co-existence in Africa with Cyprinoids proves only that that continent is nearer to the original centre, from which the distribution of Cyprinoids commenced than tropical America. The family includes herbivorous as well as strictly carnivorous forms; some are toothless, whilst others possess a most formidable dentition. The family contains so many diversified forms as to render a subdivision into groups necessary. They have not yet been obtained in fossiliferous strata.

I. ERYTHRININA.--_Adipose fin absent._

The sixteen species of this group belong to the fauna of tropical America, and are referred to the genera _Macrodon_, _Erythrinus_, _Lebiasina_, _Nannostomus_, _Pyrrhulina_, and _Corynopoma_.

II. CURIMATINA.--_A short dorsal and an adipose fin; dentition imperfect. Tropical America._

CURIMATUS.--Dorsal fin placed nearly in the middle of the body;
anal rather short or of moderate length; ventrals below the
dorsal. Body oblong or elevated, with the belly rounded or
flattened before the ventrals. Cleft of the mouth transverse,
lips none, margins of the jaws trenchant. No teeth whatever.
Intestinal tract very long and narrow.

About twenty species are known, of rather small size.

The other genera of this group have teeth, but they are either rudimentary or absent in some part of the jaws: _Prochilodus_, _Cænotropus_, _Hemiodus_, _Saccodon_, _Parodon_.

III. CITHARININA.--_A rather long dorsal and an adipose fin; minute labial teeth. Tropical Africa._

One genus only, _Citharinus_, with two species, is known. Common in the Nile, attaining to a length of three feet.

IV. ANASTOMATINA.--_A short dorsal and an adipose fin; teeth in both jaws well developed; the gill-membranes grown to the isthmus; nasal openings remote from each other. Tropical America._

LEPORINUS.--Dorsal fin placed nearly in the middle of the length
of the body; anal short; ventrals below the dorsal. Body oblong,
covered with scales of moderate size; belly rounded. Cleft of
the mouth small, with the lips well developed; teeth in the
intermaxillary and mandible, few in number, flattened, with the
apex more or less truncated, and not serrated; the middle pair
of teeth is the longest in both jaws; palate toothless.

This genus is generally distributed in the rivers east of the Andes; about twenty species are known, some of which, like _L. frederici_, _L. megalepis_, are very common. They are well marked by black bands or spots, and rarely grow to a length of two feet, being generally much smaller.--The other genera belonging to this group are _Anastomus_ and _Rhytiodus_.

V. NANNOCHARACINA.--_A short dorsal and an adipose fin; teeth in both jaws well developed; notched incisors. The gill-membranes are grown to the isthmus. Nostrils close together._

One genus, _Nannocharax_, with two species only, from the Nile and Gaboon; very small.

VI. TETRAGONOPTERINA.--_A short dorsal and an adipose fin; the teeth in both jaws well developed, compressed, notched, or denticulated; the gill-membranes free from the isthmus, and the nasal openings close together. South America and Tropical Africa._

ALESTES.--The dorsal fin is placed in the middle of the length
of the body, above or behind the ventrals; anal fin rather
long. Body oblong, covered with scales of moderate or large
size; belly rounded. Cleft of the mouth rather small. Maxillary
teeth none; intermaxillary teeth in two series; those of the
front series more or less compressed, more or less distinctly
tricuspid; the teeth of the hinder series are broad, molar-like,
each armed with several pointed tubercles. Teeth in the
lower jaw in two series; those in the front series laterally
compressed, broader behind than in front; the hinder series is
composed of two conical teeth. All the teeth are strong, few in
number.

Fourteen species from Tropical Africa; several inhabit the Nile, of which the “Raches” (_A. dentex_ and _A. kotschyi_) are the most common.

TETRAGONOPTERUS.--The dorsal fin is placed in the middle
of the length of the body, above or immediately behind the
ventrals; anal fin long. Body oblong or elevated, covered with
scales of moderate size; belly rounded. Cleft of the mouth of
moderate width. Anterior teeth strong, lateral teeth small.
Intermaxillary and mandibulary teeth subequal in size, with
a compressed and notched crown, the former in a double, the
latter in a single series; maxillary with a few teeth near its
articulation, rarely with the entire edge denticulated.

Of all the genera of this family _Tetragonopterus_ is represented by the greatest number of species; about fifty are known. Some of them seem to have a very wide range, whilst others are merely local. All are of small size, rarely exceeding a length of eight inches.

CHIRODON.--Dorsal fin placed in the middle of the length of the
body, behind the ventrals; anal long or of moderate length. Body
oblong, covered with scales of moderate size; lateral line not
continued to the tail. Belly rounded before the ventrals. Cleft
of the mouth narrow, maxillary short. A single series of small
serrated teeth in the intermaxillary and mandibulary; maxillary
teeth none.

Three species of small size from various parts of South America; the species figured is represented of the natural size, and comes from the Upper Amazons.

MEGALOBRYCON.--Dorsal fin placed in middle of the length of
the body, immediately behind the ventrals. Anal long. Abdomen
rounded in front of, and somewhat compressed behind, the
ventrals. Cleft of the mouth of moderate width. Teeth notched,
in a triple series in the intermaxillary, and in a single in the
maxillary and mandible; no other teeth behind the mandibulary
teeth or on the palate. Scales of moderate size, with the free
portion striated.

One species from the Upper Amazons (_M. cephalus_). Specimens more than one foot long have been obtained.

GASTROPELECUS.--Dorsal fin placed behind the middle of the
length of the body, above the anal; anal long; pectoral long;
ventrals very small or rudimentary. Body strongly compressed,
with the thoracic region dilated into a sub-semicircular disk.
Scales of moderate size. Lateral line descending obliquely
backwards towards the origin of the anal fin. The lower profile
compressed into an acute ridge. Cleft of the mouth of moderate
width; teeth compressed, tricuspid, in one or two series in the
intermaxillary, and in a single in the mandible; maxillary with
a few minute conical teeth; palate toothless.

Three specimens of this singular form are known from Brazil and the Guyanas; they are of very small size.

The majority of the other genera belonging to this group are South American, viz. Piabucina, Scissor, _Pseudochalceus_, _Aphyocharax_, _Chalceus_, _Brycon_, _Chalcinopsis_, _Bryconops_, _Creagrutus_, _Chalcinus_, _Piabuca_, _Paragoniates_, and _Agoniates_; two only are African, viz. _Nannæthiops_, which represents the South American _Tetragonopterus_, and _Bryconæthiops_, which is allied to Brycon.

VII. HYDROCYONINA.--_A short dorsal and an adipose fin_; _teeth in both jaws well developed and conical; gill membranes free from the isthmus; nasal openings close together. South America and Tropical Africa. Fishes of prey._

HYDROCYON.--The dorsal fin is in the middle of the length of the
body, above the ventrals; anal of moderate length. Body oblong,
compressed, covered with scales of moderate size; belly rounded.
Cleft of the mouth wide, without lips; the intermaxillaries and
mandibles are armed with strong pointed teeth, widely set and
few in number; they are received in notches of the opposite
jaw, and visible externally when the mouth is closed. Palate
toothless. Cheeks covered with the enlarged sub-orbital bones.
Orbit with an anterior and posterior adipose eyelid. Intestinal
tract short.

Four species from Tropical Africa; two occur in the Nile, _H. forskalii_ being abundant, and well known by the names “Kelb el bahr” and “Kelb el moyeh.” Their formidable dentition renders them most destructive to other fishes; they grow to a length of four feet.

CYNODON.--Dorsal fin placed behind, or nearly in, the middle of
the length of the body, behind the ventrals; anal long. Head
and body compressed, oblong, the latter covered with very small
scales; belly compressed, keeled. Teeth in the intermaxillary,
maxillary, and mandible in a single series, conical, widely set,
of unequal size; a pair of very large canine teeth anteriorly
in the lower jaw, received in two grooves on the palate; palate
with patches of minute granulated teeth. The outer branchial
arch without gill-rakers, but with very short tubercles.

Four species from Brazil and the Guyanas; they are as formidable fishes of prey as the preceding, and grow to the same size.

With the exception of _Sarcodaces_, all the remaining genera of this group belong to the fauna of Tropical America, viz. _Anacyrtus_, _Hystricodon_, _Salminus_, _Oligosarcus_, _Xiphorhamphus_, and _Xiphostoma_.

VIII. DISTICHODONTINA.--_Dorsal fin rather elongate; adipose fin present. Gill-membranes attached to the isthmus; belly rounded. Tropical Africa._

The species, ten in number, belong to one genus only (_Distichodus_), well known on the Nile under the name of “Nefasch.” They grow to a considerable size, being sometimes four feet long and one and a half foot deep. They are used as food.

IX. ICHTHYBORINA.--_An adipose fin; number of dorsal rays increased (12–17); gill-membranes free from the isthmus. Belly rounded; canine teeth. Tropical Africa._

Two genera only: _Ichthyborus_ from the Nile, and _Phago_ from West Africa. Small fishes of very rare occurrence.

X. CRENUCHINA.--_Dorsal fin rather elongate; an adipose fin. Gill-membranes free from the isthmus, with the belly rounded, and without canine teeth._

This small group is represented in the Essequibo by a single species, _Crenuchus spilurus_, and by another in West Africa, _Xenocharax spilurus_.

XI. SERRASALMONINA.--_Dorsal fin rather elongate; an adipose fin. Gill-membranes free from the isthmus; belly serrated. Tropical America._

Although the fishes of this family do not attain any considerable size, the largest scarcely exceeding two feet in length, their voracity, fearlessness, and number renders them a perfect pest in many rivers of tropical America. In all, the teeth are strong, short, sharp, sometimes lobed incisors, arranged in one or more series; by means of them they cut off a mouthful of flesh as with a pair of scissors; and any animal falling into the water where these fishes abound is immediately attacked and cut in pieces in an incredibly short time. They assail persons entering the water, inflicting dangerous wounds before the victims are able to make their escape. In some localities it is scarcely possible to catch fishes with the hook and line, as the fish hooked is immediately attacked by the “Caribe” (as these fishes are called), and torn to pieces before it can be withdrawn from the water. The Caribes themselves are rarely hooked, as they snap the hook or cut the line. The smell of blood is said to attract at once thousands of these fishes to a spot. They are most abundant in the Brazils and Guyanas; some forty species are known, and referred to the genera _Mylesinus_, _Serrasalmo_, _Myletes_, and _Catoprion_.

SIXTH FAMILY--CYPRINODONTIDÆ.

_Head and body covered with scales; barbels none. Margin of the upper jaw formed by the intermaxillaries only. Teeth in both jaws; upper and lower pharyngeals with cardiform teeth. Adipose fin none; dorsal fin situated on the hinder half of the body. Stomach without blind sac; pyloric appendages none. Pseudobranchiæ none; air-bladder simple, without ossicula auditus._

Small fishes, inhabiting fresh, brackish, and salt water of Southern Europe, Africa, Asia, and America. The majority are viviparous; and to facilitate copulation the anal fin of the adult male of many species is modified into a copulatory organ, which is probably (partially at least) introduced into the vulva of the female; but it is uncertain whether it serves to conduct the semen, or merely to give the male a firmer hold of the female during the act. Also secondary sexual differences are developed in the Cyprinodonts; the males are always the smaller, sometimes several times smaller than the females, quite diminutive; and they are perhaps the smallest fishes in existence. The fins generally are more developed in the males, and the coloration is frequently different also. Some species are carnivorous; others live on the organic substances mixed with mud. Fossil remains have been found in tertiary strata, all apparently referable to the existing genus _Cyprinodon_; they occur near Aix in Provence, in the marl of Gesso, St. Angelo, in the Brown coal near Bonn, near Frankfort, and in the freshwater-chalk of Oeningen. In the latter locality a _Poecilia_ occurs likewise.

The genera can be divided into two groups:

I. CYPRINODONTIDÆ CARNIVORÆ.--_The bones of each ramus of the mandible are firmly united; intestinal tract short, or but little convoluted. Carnivorous or insectivorous._

CYPRINODON.--Cleft of the mouth small, developed laterally and
horizontally. Snout short. Teeth of moderate size, incisor-like,
notched, in a single series. Scales rather large. Origin of the
anal fin behind that of the dorsal in both sexes, both fins
being larger in the male than in the female. Anal not modified
into a sexual organ.

Seven species occur in the Mediterranean region, all of which seem able to live in briny springs or pools, the water of which contains a much greater percentage of salts than sea-water, as the brine-springs near the Dead Sea or in the Sahara. They are as little affected by the high temperature of some of these springs (91°), for instance of that at Sidi Ohkbar in the Sahara. Like other fishes living in limited localities or concealing themselves in mud, Cyprinodonts lose sometimes their ventral fins; such specimens have been described as _Tellia_. The species of the New World are less known than those of the Old, but not less numerous.

Allied to Cyprinodon are _Fitzroyia_ from Monte Video, and _Characodon_ from Central America.

HAPLOCHILUS.--Snout flat, both jaws being much depressed, and
armed with a narrow band of villiform teeth. Body oblong,
depressed anteriorly, compressed posteriorly. Dorsal fin short,
commencing behind the origin of the anal, which is more or less
elongate.

Twenty species from the East Indies, tropical Africa, and temperate and tropical America.

FUNDULUS.--Cleft of the mouth of moderate width, developed
laterally and horizontally. Snout of moderate length. Teeth
in a narrow band, those of the outer series being largest,
conical. Scales of moderate size. Dorsal fin commencing before
or opposite the origin of the anal. Sexes not differentiated.

“Killifish,” abundant in the New World, where about twenty species have been found; _F. heteroclitus_, _majalis_, _diaphanus_, being common on the Atlantic coast of the United States; from the Old World two species only are known, viz. _F. hispanicus_ from Spain, and _F. orthonotus_ from the east coast of Africa. Allied to _Fundulus_ are the South American _Limnurgus_, _Lucania_, _Rivulus_, and _Cynolebias_.

ORESTIAS.--Ventral fins none. Cleft of the mouth of moderate
width, directed upwards, with the lower jaw prominent, and with
the upper protractile. Both jaws with a narrow band Of small
conical teeth. Scales rather small or of moderate size, those
on the head and upper part of the trunk frequently enlarged,
plate-like, and granulated. Dorsal and anal fins moderately
developed, opposite to each other. Sexes not differentiated by
modification of the anal fin. The gill-membranes of both sides
are united for a short distance, and not attached to the isthmus.

Inhabitants of Lake Titicaca and other elevated sheets of water on the Cordilleras of Peru and Bolivia, between the 14th and 19th degrees of latitude, at an elevation of 13,000 and 14,000 feet above the level of the sea. Singularly, the fishes of this outlying genus attain to a greater size than any other members of this family, being about eight inches long and comparatively bulky. They are considered a delicacy. Six species.

JENYNSIA.--Cleft of the mouth small, developed laterally and
horizontally; snout not produced. Both jaws with a series of
tricuspid teeth of moderate size. Scales of moderate size.
The origin of the anal fin is, in both sexes, behind that of
the dorsal, although the anal of the male is modified into an
intromittent organ, in which scarcely any of the rays remain
distinct.

One species from Maldonado.

GAMBUSIA.--Cleft of the mouth developed laterally and
horizontally. Snout not produced, with the lower jaw more or
less prominent. Both jaws with a band of teeth, those of the
outer series being strongest and conical. Scales rather large.
Origin of the anal fin more or less in advance of that of the
dorsal. Anal fin of the male modified into an intromittent organ
and much advanced.

Eight species from the West Indies and the southern parts of South America.--Allied genera are the Central American _Pseudoxiphophorus_ and _Belonesox_.

ANABLEPS.--Head broad and depressed, with the supraorbital
part very much raised. Body elongate, depressed anteriorly
and compressed posteriorly. Cleft of the mouth horizontal, of
moderate width, the mandible being short; upper jaw protractile.
Both jaws armed with a band of villiform teeth, those of the
outer series being largest and somewhat movable. The integuments
of the eye are divided into an upper and lower portion by a
dark-coloured transverse band of the conjunctiva; also the pupil
is completely divided into two by a pair of lobes projecting
from each side of the iris. Scales rather small or of moderate
size. Dorsal and anal fins short, the former behind the latter.
The anal fin of the male is modified into a thick and long scaly
conical organ with an orifice at its extremity.

Three species from tropical America. They are the longest Cyprinodonts, attaining to the length of nearly twelve inches. Their peculiar habit of swimming with part of the head out of the water has been noticed above (p. 113).

II. CYPRINODONTIDÆ LIMNOPHAGÆ.--_The bones of each ramus of the mandible are but loosely joined; intestinal tract with numerous circumvolutions. Sexes differentiated. Mud-eating. Tropical America._

POECILIA.--Cleft of the mouth small, transverse; mandible very
short. Both jaws with a narrow band of minute teeth. Scales
rather large. Origin of the anal fin generally nearly opposite
to that of the dorsal fin in the female, but in the male it is
modified into an intromittent organ and much advanced. Dorsal
fin short, with not more than eleven rays.

Sixteen species.

MOLLIENESIA.--Differing from _Poecilia_ in having a larger
dorsal fin, with twelve or more rays.

Five species. The males are most beautifully coloured, and their dorsal fin is much enlarged. In one species (_M. hellerii_), besides, the lower caudal rays of the mature male are prolonged into a long, sword-shaped, generally black and yellow appendage.

Two other genera belong to this group: _Platypoecilus_ and _Girardinus_.

SEVENTH FAMILY--HETEROPYGII.

_Head naked; body covered with very small scales; barbels none. Margin of the upper jaw formed, by the intermaxillaries. Villiform teeth in the jaws and on the palate. Adipose fin none. Dorsal fin belonging to the caudal portion of the vertebral column, opposite to the anal. Ventral fins rudimentary or absent. Vent situated before the pectorals. Stomach coecal; pyloric appendages present. Pseudobranchiæ none; air-bladder deeply notched anteriorly._

To this small family, which is closely allied to the Cyprinodonts and Umbridæ, belongs the famous Blind Fish of the Mammoth Cave in Kentucky, _Amblyopsis spelæus_. It is destitute of external eyes, and the body is colourless; although the eyes, with the optic nerve, are quite rudimentary, the optic lobes are as much developed as in fishes with perfect eyes. The loss of vision is compensated by the acuteness of its sense of hearing, as well as by a great number of tactile papillæ, arranged on transverse ridges on the head, and provided with nervous filaments coming from the fifth pair. The ovary is single, and the fish is viviparous, like the Cyprinodonts. It seems to occur in all the subterranean rivers that flow through the great limestone region underlying the carboniferous rocks in the central portion of the United States. As in _Cyprinodon_, so in this genus, specimens occur without ventral fins; they have been called _Typhlichthys_. The largest size to which _Amblyopsis_ grows is five inches.

_Chologaster_ is closely allied, but provided with small external eyes; its body is coloured, but it is destitute of ventrals. It was found once in a rice field in South Carolina.

[See Tellkampf, Müll. Arch. 1844, p. 381; Packard and Putnam,
“The Mammoth Cave and its Inhabitants.” Salem. 1872. 8^o.]

EIGHTH FAMILY--UMBRIDÆ.

_Head and body covered with scales; barbels none. Margin of the upper jaw formed by the intermaxillaries mesially, and by the maxillaries laterally. Adipose fin none; the dorsal fin belongs partly to the abdominal portion of the vertebral column. Stomach siphonal; pyloric appendages none; pseudobranchiæ glandular, hidden; air-bladder simple._

Two small species only are known: _Umbra krameri_ from Austria and Hungary, and _Umbra limi_, locally distributed in the United States; called “Hunds-fish” in Germany, “Dog-fish” or “Mud-fish” in America.

NINTH FAMILY--SCOMBRESOCIDÆ.