The single species, P. folium, occurs in the Mississippi, and grows to a length of about six feet, of which the rostral shovel takes about one-fourth; in young examples it is comparatively still longer.

Psephurus gladius inhabits the Yan-tse-Kiang and Hoangho, the distribution of the Polyodontidæ being perfectly analogous to that of Scaphirhynchus. It grows to an immense size, specimens of 20 feet in length being mentioned by Basilewsky. The function of the rostral process in the economy of these fishes is not yet sufficiently explained. Martens believes that it serves as an organ of feeling, the water of those large Asiatic and American rivers being too turbid to admit of the Sturgeon seeing its prey, which consists of other fishes. The eyes of Psephurus, as well as Polyodon, are remarkably small. Both fishes are used as food.

Allied to the Polyodontidæ, and likewise provided with a paddle-shaped production of the fore part of the head, is the fossil genus Chondrosteus, remains of which occur in the Lias.

FIFTH SUB-ORDER—POLYPTEROIDEI.

Paired fins with axial skeleton, fringed; dorsal fins two or more. Branchiostegals absent, but generally gular plates. Vertebral column diphycercal or heterocercal. Body scaly.

First Family—Polypteridæ.

Scales ganoid; fins without fulcra. A series of dorsal spines, to each of which an articulated finlet is attached; anal placed close to the caudal fin, the vent being near the end of the tail. Abdominal portion of the vertebral column much longer than the caudal.

This Ganoid is confined to tropical Africa, occurring in abundance in the rivers of the west coast and in the Upper Nile; but it has not been found in the river-systems belonging to the Indian Ocean. It is scarce in the Middle and Lower Nile, and the specimens found below the Cataracts have been carried down, from southern latitudes, and do not propagate their species in that part of the river. There is only one species known, Polypterus bichir (“Bichir” being its vernacular name in Egypt), which varies in the number of the dorsal finlets, the lowest being eight, the highest eighteen. It attains to a length of four feet. Nothing is known of its mode of life, and observations thereon are very desirable.

C. calabaricus, a dwarf form from Old Calabar.

Second Family—Saurodipteridæ.

Scales ganoid, smooth like the surface of the skull. Two dorsal fins; paired fins obtusely lobate. Teeth conical. Caudal heterocercal.

Extinct. Diplopterus, Megalichthys, and Osteolepis from Devonian and Carboniferous formations.

Third Family—Coelacanthidæ.

Scales cycloid. Two dorsal fins, each supported by a single two-pronged interspinous bone; paired fins obtusely lobate. Air-bladder ossified; notochord persistent, diphycercal.

Extinct. Coelacanthus from carboniferous strata; several other genera, from the coal formations to the chalk, have been associated with it—Undina, Graphiurus, Macropoma, Holophagus, Hoplopygus, Rhizodus.

Fourth Family—Holoptychiidæ.

Scales cycloid or ganoid, sculptured. Two dorsal fins; pectorals narrow, acutely lobate; dentition dendrodont.

Extinct. In this family a peculiar type of dentition is found—the jaws are armed with two kinds of teeth, small ones serially arranged, and much larger fang-like teeth disposed at long intervals. Both kinds show at their base in transverse sections a labyrinthic complexity of structure, numerous fissures radiating from the central mass of vasodentine which fills up the pulp cavity, and sending off small ramifying branches. Genera belonging to this family are Holoptychius, Saurichthys, Glyptolepis, Dendrodus, Glyptolaemus, Glyptopomus, Tristichopterus, Gyroptychius, Strepsodus, from Devonian and Carboniferous strata.

SIXTH SUB-ORDER—PYCNODONTOIDEI.

Body compressed, high and short or oval, covered with rhombic scales arranged in decussating pleurolepidal lines. Notochord persistent. Paired fins without axial skeleton. Teeth on the palate and hinder part of the lower jaw molar-like. Branchiostegals, but no gular plates.

Extinct. The regular lozenge-shaped pattern of the integuments of these fishes is described by Sir P. Egerton thus: “Each scale bears upon its inner anterior margin a thick solid bony rib, extending upwards beyond the margin of the scale, and sliced off obliquely, above and below, on opposite sides, for forming splices with the corresponding processes of the adjoining scales. These splices are so closely adjusted that, without a magnifying power or an accidental dislocation, they are not perceptible. When in situ, and seen internally, these continuous lines decussate with the true vertebral apophyses.” In some genera the “pleurolepidal” lines are confined to the anterior part of the side.

First Family—Pleurolepidæ.

Homocercal. Body less high. Fins with fulcra.

Pleurolepis and Homoeolepis from the Lias.

Second Family—Pycnodontidæ.

Homocercal. The neural arches and ribs are ossified; the roots of the ribs are but little expanded in the older genera, but enlarged in the tertiary forms, so as to simulate vertebræ. Paired fins not lobate. Obtuse teeth on the palate and the sides of the mandible; maxilla toothless; incisor-like teeth in the intermaxillary and front of the mandible. Fulcra absent in all the fins.

These fishes abound in Mesozoic and Tertiary formations. Gyrodus, Mesturus, Microdon, Coelodus, Pycnodus, Mesodon, are some of the genera distinguished by palæontologists. (See Fig. 102, p. 201.)

SEVENTH SUB-ORDER—LEPIDOSTEOIDEI.

Scales ganoid, rhombic; fins generally with fulcra; paired fins not lobate. Præ- and inter-operculum developed; generally numerous branchiostegals, but no gular plate.

First Family—Lepidosteidæ.

Scales ganoid, lozenge-shaped. Skeleton completely ossified; vertebræ convex in front and concave behind. Fins with fulcra; dorsal and anal composed of articulated rays only, placed far backwards, close to the caudal. Abdominal part of the vertebral column much longer than caudal. Branchiostegals not numerous, without enamelled surface. Heterocercal.

Fishes of this genus existed already in Tertiary times; their remains have been found in Europe as well as North America. In our period they are limited to the temperate parts of North America, Central America, and Cuba. Three species can be distinguished which attain to a length of about six feet. They feed on other fishes, and their general resemblance to a pike has given to them the vernacular names of “Gar-Pike,” or “Bony Pike.”

Second Family—Sauridæ.

Body oblong, with ganoid scales; vertebræ not completely ossified; termination of the vertebral column homocercal; fins generally with fulcra. Maxillary composed of a single piece; jaws with a single series of conical pointed teeth. Branchiostegals numerous, enamelled, the anterior broad gular plates.

Extinct. Numerous genera occur in Mesozoic formations; one with the widest range is Semionotus, with distichous fulcra, from the Lias and Jura; Eugnathus, with large posteriorly serrated scales, and fulcra on nearly all fins; Cephenoplosus from the Upper Lias; Macrosemius from the Oolite; Propterus, Ophiopsis, Pholidophorus, Pleuropholis, Pachycormus, Oxygnathus, Ptycholepis, Conodus, Eulepidotus, Lophiostomus, etc.

Third Family—Stylodontidæ.

Body rhombic or ovate, with ganoid scales; vertebræ not completely ossified; termination of the vertebral column homocercal; fins with fulcra. Maxillary composed of a single piece; jaws with several series of teeth, the outer ones equal, styliform. Dorsal fin very long, extending to the caudal. Branchiostegals numerous.

Extinct. Tetragonolepis from the Lias (see Fig. 103, p. 207).

Fourth Family—Sphærodontidæ.

Body oblong, with rhombic ganoid scales; vertebræ ossified, but not completely closed; homocercal; fins with fulcra. Maxillary composed of a single piece; teeth in several series, obtuse; those on the palate globular. Dorsal and anal fins short. Branchiostegals.

Extinct. The type genus of this family is Lepidotus, so named from its large rhombic, dense, and polished scales. The dorsal is opposite to the anal, and all the fins are provided with a double row of fulcra. This genus ranges from the Lias to the Chalk; one species would seem to have survived into tertiary times, if it should not prove to be a Lepidosteus.

Fifth Family—Aspidorhynchidæ.

Body elongate, with ganoid scales; jaws prolonged into a beak; termination of the vertebral column homocercal. Fins with fulcra; a series of enlarged scales along the side of the body. Dorsal fin opposite to the anal.

Extinct; mesozoic. Aspidorhynchus has the upper jaw longer than the lower; very peculiar is the occurrence of a single, solid, conical bone, situated in front of the symphysis of the lower jaw, to which it is joined by a suture. Belonostomus with both jaws of equal length.

Sixth Family—Palæoniscidæ.

Body fusiform, with rhombic ganoid scales. Notochord persistent, with the vertebral arches ossified. Heterocercal. All the fins with fulcra; dorsal short. Branchiostegals numerous, the foremost pair forming broad gulars. Teeth small, conical, or cylindrical.

Extinct. Many genera are known; from the Old Red Sandstone—Chirolepis and Acrolepis; from Carboniferous rocks—Cosmoptychius, Elonichthys, Nematoptychius, Cycloptychius, Microconodus, Gonatodus, Rhadinichthys, Myriolepis, Urosthenes; from the Permian—Rhabdolepis, Palæoniscus, Amblypterus and Pygopterus; from the Lias—Centrolepis, Oxygnathus, Cosmolepis, and Thrissonotus.

Seventh Family—Platysomidæ.

Body generally high, compressed, covered with rhombic ganoid scales arranged in dorso-ventral bands. Notochord persistent, with the vertebral arches ossified. Heterocercal; fins with fulcra; dorsal fin long, occupying the posterior half of the back. Branchiostegals numerous. Teeth tubercular or obtuse.

Extinct. From Carboniferous and Permian formations—Eurynotus, Benedenius, Mesolepis, Eurysomus, Wardichthys, Chirodus (M’Coy), Platysomus.

[See Traquair, “On the Structure and Affinities of the Platysomidæ”, in “Trans. Roy. Soc.,” Edinb., vol. xxix.]

EIGHTH SUB-ORDER—AMIOIDEI.

Vertebral column more or less completely ossified, heterocercal. Body covered with cycloid scales. Branchiostegals present.

First Family—Caturidæ.

Notochord persistent, with partially ossified vertebræ; homocercal; fins with fulcra. Teeth in a single series, small, pointed.

Extinct. Caturus from the Oolite to the Chalk.

Second Family—Leptolepidæ.

Scales cycloid. Vertebræ ossified; homocercal; fins without fulcra; dorsal short. Teeth minute, in bands, with canines in front.

Extinct, and leading to the living representative of this suborder. Thrissops with the dorsal fin placed far backwards, and opposite to the long anal. Leptolepis with the dorsal fin opposite to the ventrals, from the Lias and Oolite. These fishes, as far as the preserved parts are concerned, cannot be distinguished from Teleosteous fishes, to which they are referred by some Palæontologists.

Third Family—Amiidæ.

Skeleton entirely ossified; a single large gular plate; homocercal; fins without fulcra; a long soft dorsal fin. Abdominal and caudal parts of the vertebral column subequal in extent. Branchiostegals numerous.

The “Bow-fin” or “Mud-fish” (A. calva) is not uncommon in many of the fresh waters of the United States; it grows to a length of two feet. Little is known about its habits; small fish, crustaceans, and aquatic insects, have been found in its stomach. Wilder has observed its respiratory actions; it rises to the surface, and, without emitting any air-bubble whatever, opens the jaws widely, and apparently gulps in a large quantity of air; these acts of respiration are more frequently performed when the water is foul or has not been changed; and there is no doubt that an exchange of oxygen and carbonic acid is effected, as in the lungs of aërial vertebrates. The flesh of this fish is not esteemed.

Fossil remains occur in tertiary deposits of North America, for instance in the Wyoming territory; they have been distinguished as Protamia and Hypamia.

SECOND SUB-CLASS—TELEOSTEI.

Heart with a non-contractile bulbus arteriosus; intestine without spiral valve; optic nerves decussating; skeleton ossified, with completely formed vertebræ; vertebral column diphycercal or homocercal; branchiæ free.[40]

The Teleostei form the majority of the fishes of the present fauna, and are the geological successors of the Palæichthyes, undoubted Teleostei not ranging farther back than the Chalk. This sub-class comprises an infinite variety of forms; and as, naturally, many Ganoid fishes lived under similar external conditions, and led a similar mode of life as certain Teleostei, we find not a few analogous forms in both series: some Ganoids resembling externally the Teleosteous Siluroids, others the Clupeoids, others the Chætodonts, others the Scombresoces, etc. But there is no direct genetic relation between those fishes, as some Naturalists were inclined to believe.

The Teleostei are divided into six orders:—

FIRST ORDER—ACANTHOPTERYGII.

Part of the rays of the dorsal, anal, and ventral fins are not articulated, more or less pungent spines. The lower pharyngeals are generally separate. Air-bladder, if present, without pneumatic duct in the adult.[41]

First Division—Acanthopterygii Perciformes.

Body more or less compressed, elevated or oblong, but not elongate; the vent is remote from the extremity of the tail, behind the ventral fins if they are present. No prominent anal papilla. No superbranchial organ. Dorsal fin or fins occupying the greater portion of the back; spinous dorsal well developed, generally with stiff spines, of moderate extent, rather longer than, or as long as, the soft; the soft anal similar to the soft dorsal, of moderate extent or rather short. Ventrals thoracic, with one spine and with four or five rays.

First Family—Percidæ.

The scales extend but rarely over the vertical fins, and the lateral line is generally present, continuous from the head to the caudal fin. All the teeth simple and conical; no barbels. No bony stay for the præoperculum.

A large family, represented by numerous genera and species in fresh waters, and on all the coasts of the temperate and tropical regions. Carnivorous.

Fossil Percoids abound in some formations, for instance, at Monte Bolca, where species of Labrax, Lates, Smerdis and Cyclopoma (both extinct), Dules, Serranus, Apogon, Therapon, and Pristipoma have been recognised. Paraperca is a genus recently discovered in the Marles of Aix-en-Provence. A species of Perca is known from the freshwater deposit of Oeningen.

The “Freshwater Perch” (Perca fluviatilis) is too familiarly known to require description. It is generally distributed over Europe and Northern Asia; and equally common in North America, there being no sufficient ground for separating specifically the specimens of the Western Hemisphere. It frequents especially still waters, and sometimes descends into brackish water. Its weight does not seem to exceed 5 lbs. The female deposits her ova, united together by a viscid matter, in lengthened or net-shaped bands, on waterplants. The number of the eggs of one spawn may exceed a million. Two other species, P. gracilis, from Canada, and P. schrenckii, from Turkestan, have been distinguished, but they are very imperfectly known. An allied genus is Siniperca, from Northern China.

These fishes represent the Freshwater Perches of the Northern Hemisphere in the fresh waters of the temperate parts of South America. Two species have been described from Patagonia, and one or two from Chili and Peru.

The “Bass” are fishes common on the coasts of Europe and the Atlantic coasts, and in the fresh waters of the United States and Canada. The three European species are almost exclusively inhabitants of the sea, entering brackish, but never fresh waters, whilst the American species, the number of which is still uncertain, seem to affect principally fresh water, although some are also found in the sea. The best known European species is Labrax lupus (see p. 41, Fig. 4), common on the British coasts. It is a voracious fish, with a remarkably large stomach, and received from the ancient Romans the appropriate name of lupus. By the Greeks it was so highly esteemed that Archestratus termed this or one of the two other closely-allied species, taken near Milet, “offspring of the gods.” They attributed to it a tender regard for its own safety; and Aristotle says that it is the most cunning of fishes; and that, when surrounded by the net, it digs for itself a channel of escape through the sand. Specimens of from two to three feet are not scarce, but its flesh is nowadays much less esteemed than in ancient times. Of the North American species Labrax lineatus and Labrax rufus are the most common.

Three well-known species belong to this genus. The Perch of the Nile and other rivers of tropical Africa (Lates niloticus); the Perch of the Ganges and other East Indian rivers, which enters freely brackish water, and extends to the rivers of Queensland (Lates calcarifer). These two species attain to a large size, the Indian species to a length of five feet. Hamilton says that “the vulgar English in Calcutta call it ‘Cockup,’ and that it is one of the lightest and most esteemed foods brought to table in that city.” Specimens two feet in length and caught in salt water are by far the best quality. The third species (Lates colonorum) is found in Australia only, and does not appear to grow to the same large size as its congeners.

Allied to Lates is Psammoperca from Australia.

This Perch (Percalabrax japonicus) is one of the most common fishes on the coasts of China, Japan, and Formosa; the Japanese name it “Zuzuki,” or “Seengo.”

Small freshwater perches, of which A. cernua, named “Pope” in England, is the most common, and has the widest distribution in Central Europe and Siberia. The two other species have a more restricted range, A. schrætzer being confined to the Danube and other rivers emptying into the Black Sea; and A. czekanowskii to Siberian rivers. This genus is not represented in the Western Hemisphere.

The “Pike-Perches” are inhabitants of many lakes and rivers of the temperate northern zone. The European species is confined to the eastern two-thirds of the continent, and one of the most esteemed freshwater fishes; it attains to a length of three or four feet, and to a weight of from 25 to 30 lbs. It has been recommended for acclimatisation in England, and there is no doubt that in certain localities it might prove a valuable addition to the native fauna; but like all its congeners it is very voracious and destructive to smaller fishes. Two other species inhabit rivers of European and Asiatic Russia, and two or three the fresh waters of North America.

Small freshwater perches abundant in the United States. Like the following genus, and some others which need not be mentioned here, they can be regarded as small, dwarfed representatives of the preceding genera. The species seem to be numerous, but have not yet been sufficiently well distinguished. The latest and best account of them is by L. Vaillant, “Recherches sur les Poissons d’eaux douces de l’Amérique septentrionale (Etheostomatidæ),” in Nouv. Archiv. du Muséum d’Hist. Nat. de Paris, ix., 1873.

Two small Perches from the Danube and some other rivers of the continent of Europe, Aspro vulgaris and A. zingel.

Numerous species are known from the West Indies and Central America. These fishes are found in fresh, brackish, and salt water, and some of the species indiscriminately enter all three kinds of water. They do not grow to any large size, but are esteemed as food.

A small and very common marine species (E. armatus) on the coast of Australia, especially New South Wales. It is readily recognised by the peculiar shape of its body, and eight black transverse bands on a whitish ground.

This, and the preceding genus, leads to the true “Sea perches,” which never, or but rarely, enter fresh water:—

About twenty species of small size are known from temperate and tropical seas.

Anthias.—Body rather short, compressed, with scales of moderate size. Teeth villiform, with small canines in both jaws; teeth on the vomer, and palatine teeth. One dorsal, generally with ten spines; anal fin with three; caudal forked. The rays of one or more fins may be prolonged. Præoperculum serrated.

About twenty species are known from temperate and tropical seas; they are mostly of small size, and agreeably coloured, pink and yellow being the predominant colours. Anthias sacer is common in the Mediterranean, and was well known to the ancients. Aristotle says that the fishers of Sponges call it sacred, because no voracious fishes came to the places which it frequented, and the diver might descend with safety.—Callanthias is a genus closely allied to Anthias.

The “Sea perches proper” are found on the shores of all temperate and tropical seas, most abundantly in the latter. A few species enter brackish and even fresh water, one having been found as high up the Ganges as the confines of Nepal. However, all spawn in the sea. The variety of species is almost infinite, about 150 being tolerably well known, and many more having been described. The distinction of the species is most difficult, and nearly impossible to those who have no opportunity of closely and long observing them in nature, as they are not only subject to great variation of colour, but also to considerable changes dependent on age. Many are most agreeably coloured, and ornamented with spots, or cross bands or longitudinal stripes; colours which become more uniform with age in those species which attain to a large size. The majority remain of rather small size, growing to a length of one or two feet; but not a few reach more than twice that length, and may even become dangerous to man. Instances of bathers having been attacked by a gigantic species not uncommon at the Seychelles and Aden are on record, the persons having died from the injuries received. Almost all the species are eatable, and many are esteemed as food. One species is common on the British coasts (S. cabrilla), and probably some of the more southern species (S. scriba and S. gigas) occasionally wander as far northwards as the British Channel. The species figured, S. altvelis, is locally distributed over nearly all the tropical parts of the Indian Ocean, and distinguished by particularly high dorsal and anal fins. Anyperodon and Prionodes are two genera closely allied to Serranus.

About thirty species from tropical seas are known. Trachypoma is allied to this genus.

Two species are known: one from the European coasts (P. cernium), and one from Juan Fernandez (P. kneri). They attain to a weight of 80 lbs. and more. The European species has the habit of accompanying floating wood, to which they are attracted by the small marine species generally surrounding such objects, and affording a supply of food. It is known by the name of “Stone-bass,” and excellent eating.

Three species are known from the Indo-Pacific; they are of small size. One, G. orientalis, is black, with six or seven white longitudinal stripes, and one of the most common coast-fishes of that ocean.

Four species are known: three from the West Indies and one from the Galapagoes Islands.

Other genera allied to the two preceding are Aulacocephalus from Mauritius, Reunion, and Japan; and Myriodon from the coasts of Australia.

The single species known (D. bifasciatum), is very common in the East Indian Archipelago, and on the coasts of Southern China and Japan. It is of small size, and ornamented with two broad black cross-bands.

About seventy species are known from tropical seas in both hemispheres, but it is noteworthy that the species with the peculiar protuberance of the interoperculum are confined to the Indo-Pacific. The coloration is much more simple than in the small-scaled Serrani, a uniform hue of greenish, pink, or red prevailing; species with longitudinal bands are scarce, but not rarely dark cross-bands or a large spot on the side occur. The majority of the species remain within very moderate dimensions, specimens exceeding three feet in length being scarce. They are generally eaten, and some of the species belong to the commonest fishes of the tropics, as M. bengalensis, chrysurus, gembra, griseus, and others.

Glaucosoma from Japan and Australia is allied to Mesoprion.

About ten species are known, inhabiting fresh waters of the coasts of the Indo-Pacific, and being especially common in the islands of this region, and also in Tropical Australia. Some live also in brackish water. Though of small size they are esteemed as food.

About twenty species are known, the distribution of which nearly coincides with Dules, but as some of the species are more or less marine, the genus is spread over the whole area of the tropical Indo-Pacific. Other species, especially those of Australian rivers, are entirely limited to fresh water. Th. theraps, Th. servus, and Th. cuvieri belong to the most common fishes of that area, extending from the east coast of Africa to Polynesia. They are readily recognised by the blackish longitudinal bands with which the body is ornamented. All the species are of small size. Helotes is closely allied to this genus.