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

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.

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.

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.

Fourteen species from Tropical Africa; several inhabit the Nile, of which the “Raches” (A. dentex and A. kotschyi) are the most common.

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.

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.

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

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.

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.

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.

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.

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

“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.

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.

One species from Maldonado.

Eight species from the West Indies and the southern parts of South America.—Allied genera are the Central American Pseudoxiphophorus and Belonesox.

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.

Sixteen species.

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.

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.

Body covered with scales; a series of keeled scales along each side of the belly. Margin of the upper jaw formed by the intermaxillaries mesially, and by the maxillaries laterally. Lower pharyngeals united into a single bone. Dorsal fin opposite the anal, belonging to the caudal portion of the vertebral column. Adipose fin none. Air-bladder generally present, simple, sometimes cellular, without pneumatic duct. Pseudobranchiæ hidden, glandular. Stomach not distinct from the intestine, which is quite straight, without appendages.

The fishes of this family are chiefly marine, some living in the open ocean, whilst others have become acclimatised in fresh water; many of the latter are viviparous, all the marine forms being oviparous. They are found in all the temperate and tropical zones. Carnivorous.

This family is represented in the strata of Monte Bolca by rare remains of a fish named Holosteus, allied to Belone or Scombresox, and by a species of Belone in the miocene of Licata.

The long upper jaw of the “Gar-pike” is formed by the intermaxillaries, which are united by a longitudinal suture. Both jaws are beset with asperities, and with a series of longer, conical-pointed, widely-set teeth. Skimming along the surface of the water, the Gar-pike seize with these long jaws small fish as a bird would seize them with its beak; but their gullet is narrow, so that they can swallow small fish only. They swim with an undulating motion of the body; although they are in constant activity, their progress through the water is much slower than that of the Mackerels, the shoals of which sometimes appear simultaneously with them on our coasts. Young specimens are frequently met in the open ocean; when very young their jaws are not prolonged, and during growth the lower jaw is much in advance of the upper, so that these young fishes resemble a Hemirhamphus. About fifty species are known from tropical and temperate seas, Belone belone being a common fish on the British coast. Its bones, like those of all its congeners, are green; and therefore the fish, although good eating, is disliked by many persons. Some species attain a length of five feet.

The “Saury” or “Skipper” resemble the Gar-pike, but the teeth in the jaws are minute; they seem to feed chiefly on soft pelagic animals. In their habits they are still more pelagic; and the young, in which the beak is still undeveloped, are met with everywhere in the open ocean, in the Atlantic as well as in the Pacific. The European species, Sc. saurus, is not rare on the British coast; four other species have been described, closely allied to Sc. saurus.

In the young both jaws are short; the upper is never prolonged, the intermaxillaries forming a triangular, more or less convex, plate. The “Half-beaks” are common between and near the tropics; some forty species are known, none of which attain to the same length as the Gar-pike, scarcely ever exceeding a length of two feet. Some of the tropical species live in fresh water only; they are of small size and viviparous.

One species (A. sclerolepis) from the coast of Queensland (not New Zealand); it may be regarded as a Hemirhamphus, with retarded development of the lower jaw.

Forty-four different kinds of “Flying-fishes” are known from tropical and sub-tropical seas; some have a very wide range, whilst others seem to remain within one particular part of the ocean; thus, the species figured, E. callopterus, has been hitherto found on the Pacific side of the isthmus of Panama only. Their usual length is about 10 or 12 inches, but specimens of 18 inches have been caught. They always live in shoals, and their numbers at certain times and localities are immense; thus, at Barbadoes many boats engage in their capture, as they are excellent eating. The pectorals are in the various species of unequal length; in some they extend to the anal fin only; in others (and these are the best fliers) to the caudal. A few have curious, barbel-like appendages at the lower jaw, which may disappear with age or be persistent throughout life. The literature on the subject of Flying-fishes is very extensive, and great diversity of opinion exists among observers as regards the mode and power of their flight; but the most reliable agree that the fishes do not leave the water for the purpose of catching insects (!), and that they are unable to move their fins in the manner of a bat or bird, or to change voluntarily the direction of their flight, or to fly beyond a very limited distance. The most recent enquiries are those of K. Möbius (“Die Bewegungen der Fliegenden Fische durch die Luft,” Leip. 1878, 8vo), the chief results of which may be summed up thus: Flying-fish are more frequently observed in rough weather and in a disturbed sea than during calm; they dart out of the water when pursued by their enemies, or frightened by an approaching vessel, but frequently also without any apparent cause, as is also observed in many other fishes; and they rise without regard to the direction of the wind or waves. The fins are kept quietly distended, without any motion, except an occasional vibration caused by the air whenever the surface of the wing is parallel with the current of the wind. Their flight is rapid, but gradually decreasing in velocity, greatly exceeding that of a ship going 10 miles an hour, and a distance of 500 feet. Generally, it is longer when the fishes fly against than with or at an angle to the wind. Any vertical or horizontal deviation from a straight line is not caused at the will of the fish, but by currents of the air; thus they retain a horizontally straight course when flying with or against the wind, but are carried towards the right or left whenever the direction of the wind is at an angle with that of their flight. However, it sometimes happens that the fish during its flight immerses its caudal fin in the water, and by a stroke of its tail turns towards the right or left. In a calm the line of their flight is always also vertically straight, or rather parabolic, like the course of a projectile, but it may become undulated in a rough sea, when they are flying against the course of the waves; they then frequently overtop each wave, being carried over it by the pressure of the disturbed air. Flying-fishes often fall on board of vessels, but this never happens during a calm, or from the lee side, but during a breeze only, and from the weather side. In daytime they avoid a ship, flying away from it; but during the night, when they are unable to see, they frequently fly against the weather-board, where they are caught by the current of air, and carried upwards to a height of 20 feet above the surface of the water, while, under ordinary circumstances, they keep close to it. All these observations point clearly to the fact that any deflection from a straight course is due to external circumstances, and not to voluntary action on the part of the fish.

Tenth Family—Esocidæ.

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 to the caudal portion of the vertebral column. Stomach without blind sac; pyloric appendages none. Pseudobranchiæ glandular, hidden; air-bladder simple; gill-opening very wide.

This family includes one genus only, Esox, the “Pikes,” inhabitants of the fresh waters of the temperate parts of Europe, Asia, and America. The European species, E. lucius, inhabits all three continents, but the North American waters harbour five, or perhaps more, other species, of which the “Muskellunge,” or “Maskinonge” (E. estor) of the Great Lakes attains to the same large size as the common Pike. The other species are generally called “Pickerell” in the United States.

Fossil Pike, belonging to the existing genus, have been found in the freshwater-chalk of Oeningen, and in the diluvial marl of Silesia. Remains of the common Pike occur in abundance in quaternary deposits.

Eleventh Family—Galaxiidæ.

Body naked, barbels none. Margin of the upper jaw chiefly formed by the intermaxillaries, which are short, and continued by a thick lip, behind which are the maxillaries. Belly rounded; adipose fin none; dorsal opposite to anal. Pyloric appendages in small number. Air-bladder large, simple; pseudobranchiæ none. The ova fall into the cavity of the abdomen before exclusion.

Small freshwater fishes of the southern hemisphere, belonging to two genera, Galaxias and Neochanna. Of the former genus five species are found in New Zealand, where this type is most developed, three in New South Wales, two in Tasmania, and four in the southern extremity of South America. Their native name in New Zealand is “Kokopu,” and they were dignified with the name of “Trout” by the settlers before the introduction of true Salmonidæ. They rarely exceed a length of eight inches. Neochanna is a degraded form of Galaxias, from which it differs by the absence of ventral fins. This fish has hitherto been found only in burrows, which it excavates in clay or consolidated mud, at a distance from water.

Twelfth Family—Mormyridæ.

Body and tail scaly; head scaleless; barbels none. The margin of the upper jaw is formed in the middle by the intermaxillaries, which coalesce into a single bone, and laterally by the maxillaries. Sub- and inter-operculum present, the latter very small. On each side of the single parietal bone a cavity leading into the interior of the skull, and covered with a thin bony lamella. All the fins are well developed, in Mormyrus; or caudal, anal, and ventral fins are absent, in Gymnarchus. No adipose fin. Pseudobranchiæ none; gill-openings reduced to a short slit. Air-bladder simple. Two coeca pylorica behind the stomach.

This family is characteristic of the freshwater fauna of tropical Africa. Of Mormyrus (including Hyperopisus and Mormyrops), fifty-one species are known, of which eleven occur in the Nile. Some attain a length of three or four feet, others remain small. Their flesh is said to have an excellent flavour. The species figured (and probably other allied species) was an object of veneration to the ancient Egyptians, and, therefore, frequently occurs in their emblematic inscriptions. They abstained from eating it because it was one of three different kinds of fishes accused of having devoured a member of the body of Osiris, which, therefore, Isis was unable to recover when she collected the rest of the scattered members of her husband.

The Mormyri possess a singular organ on each side of the tail, 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 Mormyri differ much with regard to the extent of the dorsal and anal fins, the former sometimes occupying the greater portion of the length of the back, sometimes being much shorter and limited to the tail. In some the snout is short and obtuse, in others long and decurved, with or without appendage.

Of Gymnarchus one species only is known, G. niloticus, which occurs in the Nile and West African rivers, and attains a length of six feet. The form of its body is eel-like, and each jaw is armed with a series of incisor-like teeth. Like Mormyrus, Gymnarchus possesses a pseudo-electric organ, thickest on the tail, tapering in front, and extending nearly to the head. It consists of four membranaceous tubes intimately connected with the surrounding muscles, and containing prismatic bodies arranged in the manner of a paternoster. The air-bladder of Gymnarchus is cellular, very extensible, and communicates with the dorsal side of the œsophagus by a duct possessing a sphincter.

Thirteenth Family—Sternoptychidæ.

Body naked, or with very thin deciduous scales; barbels none. Margin of the upper jaw formed by the maxillary and intermaxillary, both of which are toothed; opercular apparatus not completely developed. Gill-opening very wide; pseudobranchiæ present or absent; air-bladder simple, if present. Adipose fin present, but generally rudimentary. Series of phosphorescent bodies along the lower parts. The eggs are enclosed in the sacs of the ovarium, and excluded by oviducts.

Pelagic and Deep-sea fishes of small size.

These small fishes are now and then picked up in the Mediterranean and Atlantic. According to the dredging-records of the “Challenger,” they and the allied genera Argyropelecus and Polyipnus would descend to depths of respectively 1100 and 2500 fathoms; but the form of their body and their whole organisation render this statement very improbable; they most likely live at a small depth during the daytime, coming to the surface at night, like many Scopelus.

Coccia and Maurolicus are two other genera allied to the preceding.