The Cling-Fishes are curious small, carnivorous, Marine Fishes, usually found between tide-marks among loose stones and shells, to which they adhere firmly by means of the adhesive ventral disk. They can live a long time out of water. About 50 species are known, from various parts of the world, extending as far north as Scotland and Vancouver Island, and southwards to New Zealand. Three or four species, belonging to the genus Lepadogaster, are known to occur on the British coasts. The principal genera are Gobiesox, Chorisochismus, Sicyases, Cotylis, Lepadogaster, Trachelochismus, Diplocrepis, Crepidogaster, and Leptopterygius.^[748]

Fam. 9. Blenniidae.—Suborbitals often forming a more or less distinct subocular shelf; mouth moderate or large, more or less protractile, often bordered to a considerable extent by the maxillaries. Most of the praecaudal vertebrae with strong transverse processes supporting the ribs, which may bear epipleurals. Gill-membranes usually attached to isthmus; 6 or 7 branchiostegal rays; gills 4, a slit behind the fourth; pseudobranchiae usually present. Post-temporal forked; scapula and coracoid more or less developed, sometimes much reduced, the former pierced by a foramen; pectoral rays attached to 4 or 5 hour-glass-shaped pterygials, one or two of which are in contact with the coracoid. Ventral fins jugular, with not more than 4 rays, or absent. Body more or less elongate, sometimes Eel-shaped, naked or with small scales. Dorsal and anal fins elongate, the former constituted entirely of spines, or anteriorly of spines or non-articulated rays, and posteriorly of soft rays. Caudal fin usually distinct, with expanded hypural.

A large family, mostly of small Marine Fishes, the arrangement of which still offers great difficulties. Whether the aberrant genera Cerdale and Ptilichthys deserve to be regarded as the types of distinct families cannot be decided until the skeleton has been examined. The species number about 350, from nearly all the seas, a few inhabiting fresh waters, and are referred to numerous genera, of which the following are the principal:—Gadopsis, Enneanectes, Heterostichus, Acanthoclinus, Clinus, Emmnion, Blennius, Chasmodes, Petroscirtes, Xiphasia, Anarrhichas, Pataecus, Salarias, Ophioblennius, Anoplarchus, Xiphistes, Opisthocentrus, Chaenopsis, Pholedichthys, Lumpenus. Remains of Clinus and Blennius have been described from the Miocene, and the extinct genus Pterygocephalus, from the Upper Eocene, is regarded as allied to Clinus.

The Blenniidae are mostly carnivorous, but a few are herbivorous; some are viviparous (Clinus), others oviparous. Species of Blennius occur in abundance on our coasts, and are among the most familiar tenants of small rock-pools. Their habits have been admirably described by Guitel.^[749] The male makes a sort of nest, and defends the brood. Numerous species of the genus Salarias occur in the tropics; these little fish, as their name implies, are remarkable for the long leaps they are able to make. The largest of the Blenniids are the "Wolf-Fishes," often named "Cat-Fishes" (Anarrhichas), of which one species (A. lupus) is common on the British coasts, growing to a length of 5 or 6 feet. "It is impossible," says Brown Goode, "to imagine a more voracious-looking animal than the Sea Cat-Fish, with the massive head and long sinuous, muscular body, its strongly rayed fins, its vice-like jaws, armed with great pavements of teeth, those in front long, strong, pointed, like those of a tiger. It has been known to attack furiously persons wading at low tide among the rock-pools." Its flesh is excellent eating, but generally despised in this country owing to the unprepossessing appearance of the animal.

Fam. 10. Batrachidae.—Suborbital arch absent; basis cranii simple; mouth very large, slightly protractile, bordered to a great extent by the maxillaries. Vertebrae numerous, 29-46 (11-12 + 17-34), without ribs, with sessile epipleurals, simulating ribs;^[750] parapophyses rudimentary or absent. Post-temporal small and ankylosed to the skull; scapula and coracoid much reduced, 4 or 5 elongate pterygials, dilated distally, the two lower in contact with the coracoid. Ventral fins jugular, with 1 spine and 2 or 3 branched rays. Gill-openings narrow, the gill-membranes broadly grown to the isthmus; gills 3; pseudobranchiae absent. Head broad and depressed; body naked or with small scales. Spinous dorsal very short, soft dorsal and anal long.

This family is on the whole intermediate between the Blenniidae and the Pediculati. Sluggish, voracious, carnivorous Fishes from the shores of tropical and warm seas, some of them ascending rivers. The species number about 20, referable to 5 genera: Batrachus, Opsanus, Thalassophryne, Thalassothia, and Porichthys. The eggs of Batrachus tau are very large, ¼ inch in diameter, and are deposited in a little retreat provided by the parent; the male assumes the care of the brood; the young fasten themselves to rocks by means of an adhesive ventral disk, which soon disappears.^[751]

In Thalassophryne, from the coasts of Central America, the opercular spine and the two dorsal spines are perforated, and convey poison from subcutaneous sacs situated at their base.^[752] In the American genus Porichthys the head and body bear series of greatly developed mucous pores, some of which simulate the photophores of Scopelus, but are not luminous.^[753]

Fam. 11. Pholididae.—Suborbitals not forming a subocular shelf; mouth scarcely protractile, with thick lips. Praecaudal vertebrae similar to the caudals, without transverse processes, with hæmal arches; ribs sessile. Gill-membranes free from the isthmus; 4 or 5 branchiostegal rays; gills 4, a slit behind the fourth; pseudobranchiae present. Scapular arch as in Blenniidae. Ventral fins jugular and rudimentary, or absent. Body elongate, compressed, with very small scales. Dorsal and anal fins elongate, the former constituted entirely of non-articulated rays or spines. Caudal fin distinct, with expanded hypuraL.

Small shore fishes of the Northern Seas, differing from the Blenniidae in the structure of the praecaudal vertebrae, in spite of the external resemblance which the two known genera, Pholis (Centronotus) and Apodichthys, bears to Anoplarchus and Xiphistes. Species about 10.

A well-known British fish of this family is the little Gunnel or Butter-Fish (Pholis gunnellus), remarkable for the manner in which the female protects her offspring, coiling herself round the eggs, which she rolls up into a ball about the size of a Brazil nut, in holes of the boring Mollusc (Pholas). The male sometimes assists the female.

Fam. 12. Zoarcidae.—Suborbitals not forming a subocular shelf; mouth feebly protractile. Praecaudal vertebrae with strong transverse processes bearing ribs and epipleurals. Gill-membranes usually more or less broadly united to isthmus; 5 to 8 branchiostegal rays; gills 4, a slit behind the fourth; pseudobranchiae present or absent. Scapular arch as in Blenniidae. Ventral fins jugular or absent; if present, with 1 to 4 rays. Body more or less elongate, naked or with very small scales. Dorsal and anal fins elongate, all the rays articulated, or a few of the posterior dorsals spinous. Usually no distinct caudal fin.

These fishes have usually been placed, in part at least, near the Gadids, but they have more in common with the Blenniids, as pointed out by Jordan and Evermann, and may be regarded as degraded forms descended from the latter.^[754] The family is widely distributed in all seas, many of the forms being specially adapted to live at great depths. The species known number about 130. Principal genera: Scytalina, Zoarces, Lycodes, Gymnelis, Lycocara, Melanostigma, Derepodichthys, Bathyonus, Porogadus, Bythitis, Neobythitis, Cataetyx, Selachophidium, Acanthonus, Typhlonus, Aphyonus, Tauredophidium, Rhodichthys, Brosmophycis, Brotula, Lucifuga, Lamprogrammus, Diplacanthopoma, Hephthocara.

Some are oviparous, others (Zoarces, Diplacanthopoma, Hephthocara, Lucifuga) viviparous. The eyes are absent, or at least not visible externally in some of the bathybial forms (Typhlonus, Aphyonus, Tauredophidium), as well as in the only known freshwater forms, the Cuban Cave-Fishes Stygicola and Lucifuga, which are evidently allied to the marine Brotula, whilst the blind Cave-Fishes of North America (cf. p. 618) are derived from freshwater types. It is believed that blind fishes are found also in caves of the island of Jamaica, but no specimens have been seen by naturalists. The largest Cuban Cave-Fish is 5 inches long.^[755]

Fam. 13. Congrogadidae.—Eel-shaped Fishes without ventrals, allied to the Blenniidae, but with all the rays soft and articulated, the post-temporal small and ankylosed to the skull, and the sub-orbitals produced into laminae supporting the eyeball. Lips much developed; gill-membranes free from isthmus; scales very small.

A single genus, Congrogadus, with three species from the Australian and East Indian coasts. The recently described Japanese genus Hierichthys has been referred to this family.

Fam. 14. Ophidiidae.—Degraded Blenniids, closely related to the Zoarcidae, with pseudobranchiae, with tapering tail without distinct caudal fin, and with the ventral fins each reduced to a pair of filaments or a bifid ray inserted just behind the chin at the extremity of the clavicle, which is produced forwards as a slender rod.

Small marine, carnivorous fishes, from the Atlantic and Southern Pacific coasts as well as from great depths in the Atlantic, Pacific, and Indian Oceans. About 25 species are known. Genera: Ophidium, Lepophidium, Genypterus.

Fam. 15. Podatelidae.—Mouth inferior, protractile, toothless or with minute teeth. Praecaudal vertebrae with transverse processes, to which the ribs are attached. Gill-membranes narrowly attached to isthmus; 8 or 9 branchiostegal rays; gills 4; no pseudobranchiae. Supratemporal loosely attached by ligament to the skull; scapula cartilaginous, perforate, bearing the base of the pectoral fin, which is an undivided cartilaginous plate; coracoid small, ossified. Ventral fins jugular, each reduced to a single stout filament made up of two intimately coherent rays. Body short, tail elongate and tapering, compressed; no scales. A short dorsal fin, without spines, situated above the pectorals; a long anal fin, continuous with the caudal.

The genus Podateles (Ateleopus) comprises only two species from the deep sea, one from Japan and one from India.

Division IX.—TAENIOSOMI.

Exceedingly compressed, more or less elongate, often ribbon-like fishes of doubtful affinities, probably related to the earlier Acanthopterygians, the ventral fins, when well developed, comprising as many as 7 to 9 rays. Dorsal fin extending from the head to the end of the tail, its rays simple (separable into lateral halves), the anterior often prolonged; anal fin very short or absent. Pectoral fin with horizontal or nearly horizontal base, the rays supported by the scapula and by three short pterygials, all three, or two at least, of which are related to the coracoid. Ribs small and slender, or absent. Post-temporal simple and solidly attached to the skull. Scales minute or absent.

Deep-sea or pelagic fishes from the Atlantic and Mediterranean and from the Pacific; the life-histories are still very imperfectly known, and great changes of form take place with growth. Only two families.^[756]

Fam. 1. Trachypteridae.—Mouth very protractile; ventral fins more or less developed, with 6 to 9 rays, or reduced to a single long ray; no anal fin; vent about the middle of the body; caudal rays, if present, divided into two fascicles, the upper sometimes much prolonged and directed upwards.

Two genera. The most generalised is Trachypterus, of which probably only 10 forms are entitled to specific distinction. The best known species is T. arcticus, the Deal-Fish or Northern Ribbon-Fish, which reaches a length of 8 feet or more, and of which a few specimens have been stranded on the coasts of Scotland. Nilsson, who has observed these fishes alive on the Scandinavian coast, says they approach the shore at flood-tide on sandy shelving bottoms, and are often left by the retreating waves; that they move with one side turned obliquely upward, and that they lie on the side like Flat-Fishes on the bottom in 2 or 3 fathoms of water. Regalecus differs in the presence of a single ray to the ventral and the absence of the caudal fin. Some 5 or 6 species may be distinguished. R. glesne, the Oar-fish, or "King of the Herrings," is the best known and the largest species, reaching a length of over 20 feet. About 25 specimens are known to have occurred on the British coasts. Some of the accounts of "Sea-Serpents" are probably based on this fish, which has been observed to swim with undulating motion and with a small portion of the head as well as the crest-like anterior part of the dorsal fin above the water.

The fish named Stylophorus chordatus, which has been referred to this family, is known from a single specimen too imperfectly preserved to afford a clear idea of its affinities.

Fam. 2. Lophotidae.—Mouth moderately protractile; ventrals very small, if distinct, with 4 or 5 rays; abdominal cavity extending nearly the whole length of the much elongated body, the vent very far back and followed by a short anal fin; caudal fin small, not divided.

A single genus, Lophotes, with 3 or 4 species, from the Mediterranean, the tropical Atlantic, the Cape of Good Hope, Japan, and New Zealand, reaching a length of 6 feet or more. The dorsal fin commences with an extremely long and strong spine on the head, which is much elevated and truncate in front.

Sub-Order 11. Opisthomi

Air-bladder without open duct. Opercle well developed, hidden under the skin; supraoccipital in contact with the frontals, separating the parietals. Pectoral arch suspended from the vertebral column, far behind the skull; no mesocoracoid. Vertical fins with spines. Ventral fins absent.

This division stands in the same relation to the Acanthopterygii as do the Apodes to the Malacopterygii. The single family is possibly derived from the Blenniidae.

Fam. 1. Mastacembelidae.—Body more or less Eel-shaped; a series of short spines detached from the very elongate dorsal fin, which is more or less confluent with the likewise very elongate anal fin. A single nostril on each side. Mouth not protractile, bordered by the praemaxillaries, to the upper border of which the maxillaries are attached. Gill-cleft inferior; gills 4; branchiostegal rays 6; no pseudobranchiae. Vertebrae numerous (72-95), the praecaudals with transverse processes bearing the ribs. Scales very small.

Carnivorous fishes, from fresh and brackish waters of Southern Asia and Tropical Africa. 33 species are known, referable to two genera: Mastacembelus and Rhynchobdella. The largest species reach a length of three feet. Little is known of their habits. Of the Indian Rhynchobdella aculeata, Day says it conceals itself in the mud and becomes drowned in water if unable to reach the surface, as it apparently requires to respire air directly.

Sub-Order 12. Pediculati.

Air-bladder without open duct. Opercle large, hidden under the skin; supraoccipital in contact with the frontals, separating the parietals. Pectoral arch suspended from the skull; no mesocoracoid. No ribs, no epipleurals. Ventral fins jugular. Gill-opening reduced to a foramen situated in or near the axil, more or less posterior to the base of the pectoral. Body naked or covered with spines or bony tubercles.

A small, natural group, connected with the Acanthopterygii Jugulares through the Batrachidae, in which the elongate pterygials of the pectoral fin foreshadow the kind of arm ("pseudobrachium") which is more or less characteristic of these highly aberrant Fishes. As in the Batrachidae, the post-temporal is flat and ankylosed to the cranium, and the suprascapula is much elongated. The pterygials, two or three in number, are separated from the small scapula and coracoid by a broad ligament, the arm-like pectorals being more or less distinctly geniculated and inserted far back behind the cranium. The head is large, the basis cranii simple. The gills are reduced to 2, 2½, or 3. The spinous dorsal, if present, consists of a few rays, which may be modified into tentacles inserted on the head. Vertebrae 17 to 31.

Five families:—

Fam. 1. Lophiidae.—Mouth extremely large, terminal, with very strong cardiform teeth. Gill-opening in lower axil of pectoral; pseudobranchiae present. Pectoral fin scarcely geniculated, with two pterygials. Ventral fin with 1 spine and 5 branched rays. Spinous dorsal present. Skin naked.

Twelve species, referable to three genera (Lophius, Chirolophius, and Lophiomus) living on the bottom of the Atlantic, Indian, and Pacific Oceans, at moderate or great depths. Lophius was represented in the Upper Eocene of Monte Bolca.

The Fishing-Frog or Angler (Lophius piscatorius) has a wide distribution, occurring on the coasts of Europe and North America. The first dorsal ray, inserted on the snout, is very long, movable in every direction, and terminates in a dermal flap, which is supposed to be used by the "Angler" as a bait, attracting other fishes, which are soon ingulfed in the enormous gape. It grows to a length of over 5 feet. The ventral rays are very elongate in the young.

Fam. 2. Ceratiidae.—Mouth extremely large, terminal, with strong cardiform teeth. Gill-opening in lower axil of pectoral; pseudobranchiae absent. Pectoral fin scarcely geniculated, with three pterygials. Ventral fins absent. Spinous dorsal fin usually present, sometimes reduced to a single tentacle on the snout. Skin naked.

The members of this family, about 25 in number, are all inhabitants of great depths (300-2600 fathoms). The colour of the body is usually a deep black, and the first dorsal spine, on the head, may terminate in a luminous bulb with or without filaments. "The Bathybial Sea-devils," writes Günther, "are degraded forms of Lophius; they descend to the greatest depths of the ocean. Their bones are of an extremely light and thin texture, and frequently other parts of their organisation, their integuments, muscles, and intestines are equally loose in texture when the specimens are brought to the surface. In their habits they probably do not differ in any degree from their surface representative, Lophius."

Principal genera: Ceratias, Aceratias, Oneirodes, Himantolophus, Aegaeonichthys, Melanocetus, Liocetus, Linophryne, Caulophryne, Dolopichthys.

Fam. 3. Antennariidae.—Mouth large, vertical or very oblique, turned upwards, with cardiform teeth. Gill-opening in or behind lower axil of pectoral; pseudobranchiae absent. Pectoral fin forming an elbow-like angle, with three pterygials. Ventral with 4 or 5 rays. Spinous dorsal present. Skin naked or spinulose.

About 40 species, referable to 5 genera: Pterophryne, Antennarius, Brachionichthys, Saccarius, and Chaunax.

The species of Antennarius live mostly in coral groves, where they lie in wait for prey, well concealed by their protective coloration and the harmonising aspect of their integument and appendages. To this genus also belongs the "Marbled Angler" (A. marmoratus), carried about in mid ocean among the Sargassum weed, to rest on which, from its peculiar arm-like pectoral fins, it is specially fitted; there it makes its wonderful nest of silk-like fibres, probably secreted by the parent as in the Sticklebacks, with large bundles of eggs hanging like grape clusters.^[757] The deep-sea Chaunax inflates its abdomen like Tetrodon.

Fam. 4. Gigantactinidae.—Mouth inferior, snout produced into a long tentacle directed forwards, and bearing a luminous organ. Body covered with small spines. Otherwise as in the Ceratiidae. Gigantactis vanhoeffeni, of Brauer, from the Indian Ocean, at depths of about 1000 fathoms.

Fam. 5. Malthidae.—Mouth rather small, subterminal or inferior, with villiform or cardiform teeth. Gill-opening above pectoral; pseudobranchiae absent. Pectoral fin forming an elbow-like angle, with three pterygials. Ventral with 5 rays. Spinous dorsal absent, or reduced to a more or less developed tentacle lodged in a cavity under the snout. Head and body with bony tubercles or spines.

About 30 species are known, mostly from the deep sea within the tropics (down to 1270 fathoms). Principal genera: Coelophrys, Malthe, Malthopsis, Halieutaea, Halicmethes, Dibranchus.

The "Bat-Fish" (Malthe vespertilio), common in shallow water about the West Indies, is said to assume an almost toad-like attitude on the ground, the head being directed slightly upwards, while the pectorals take on the function of hind legs and the ventrals of fore legs.

Sub-Order 13. Plectognathi.

Air-bladder without open duct. Opercular bones more or less reduced; supraoccipital in contact with the frontals, separating the parietals; maxillary and praemaxillary bones often firmly united. Pectoral arch suspended from the skull. No ribs. Ventral fins thoracic and much reduced if present; the pelvic bones, if present, more or less completely co-ossified. Gill-opening much reduced. Body covered with more or less osseous scales, bony scutes, or spines, or naked.

A highly aberrant group, closely connected with the Acanthopterygii through the Acanthuridae, as pointed out long ago by Dareste.^[758] The skeleton is often feebly ossified and the vertebrae much reduced in number, but the jaws, although short, are very strong, usually with large sectorial teeth which may be confluent into a beak; the post-temporal is short and simple, suturally united to the squamosal. These fishes have usually been arranged in three divisions: Sclerodermi, Ostracodermi, and Gymnodontes, but Regan,^[759] whose classification is here followed, has shown that the latter include a type (Triodon) which, in spite of its beak-like teeth, is more nearly related to the Sclerodermi, whilst the Ostracodermi have much more in common with the latter than with the Gymnodontes. It therefore appears best to admit only two divisions, the first with 4, the second with 3 families:—

Division I.—SCLERODERMI.

Supraclavicle vertical; pectoral pterygials not enlarged, movably attached by ligament to the scapula and coracoid, three to the former and one to the latter. All the vertebrae with the neural arches forming a single spine. Basis cranii more or less distinctly double; dentary and articular completely co-ossified.

Fam. 1. Triacanthidae.—Praemaxillaries protractile, free from the maxillaries; teeth in the jaws separate, conical or incisor-like; palatine arch firmly united to the skull. Gills 4. Praecaudal vertebrae with parapophyses; epipleurals present. Spinous dorsal fin with 2 to 6 spines. Ventral fins each represented by a strong spine, with an inner basal knob which locks it when everted, rarely with the addition of 1 or 2 rudimentary soft rays; pelvis present, firmly united to the pectoral arch. Scales small, sometimes spinous or bony. Vertebrae 20.

Marine fishes from the Indian and Western Pacific Oceans. Ten species, referable to three genera: Triacanthus, Triacanthodes, Halimochirurgus. The latter, remarkable for its long, tube-like snout, is the only deep-sea form of this Sub-order; it was recently discovered in the Gulf of Manaar, at a depth of 143 fathoms. Fossil genera are Acanthopleurus, Oligocene, and Spinacanthus, Eocene.

Fam. 2. Triodontidae.—Praemaxillaries not protractile, firmly united to the maxillaries; teeth coalescent into a beak, the upper jaw divided by a median suture, the lower simple. Praecaudal vertebrae with or without parapophyses; epipleurals present. No spinous dorsal fin. No ventral fins. Abdomen with a dilatable sac, kept expanded by the very long movable pelvis. Body covered with small, spiny, subimbricate, bony laminae. Vertebrae 20.

A single species, the curious Triodon bursarius of the Indian Ocean and Archipelago.

Fam. 3. Balistidae.—Praemaxillaries not protractile, firmly united to the praemaxillaries; teeth incisor-like; palatine movably articulated with ectopterygoid, or entirely free from it. Gills 4. Praecaudal vertebrae with well-developed parapophyses, to which epipleurals are attached. Spinous dorsal fin with 1 to 3 spines. Ventral fins, if present, represented by a single short rough spine at the end of the long, movable pelvis. Body covered with juxtaposed movable scutes or with minute rough scales.

About 100 species are known from the tropical and warm seas, one species (Balistes capriscus) occasionally wandering as far north as the south coast of England. Genera: Balistes, Monacanthus, Paraluteres, Pseudaluteres, Pseudomonacanthus, Aluteres, Psilocephalus. The Oligocene genus Acanthoderma is closely allied to Balistes.

The "File-Fishes" or "Trigger-Fishes" (Balistes), the largest species of which grow to nearly 3 feet, have a powerful dentition, which enables them to break off pieces of corals, on which they feed, and to bore holes in the hard shells of Mollusca in order to extract the soft parts; they are themselves well protected by a mail of hard, rhomboidal scales. The herbivorous Monacanthus is less favoured in this respect, the rough scales being so small as to give the skin a velvety appearance.

Psilocephalus differs from Monacanthus in its very elongate head and body, the very feeble dorsal spine, the presence of a mental barbel, and its more numerous vertebrae (29 or 30 instead of 18 to 21). The flesh of many of these fishes is poisonous.^[760] The drumming sounds produced by Balistes have been described by Möbius.^[761]

Fam. 4. Ostraciontidae.—Praemaxillaries not protractile, firmly united to the praemaxillaries; teeth incisor-like; palatine immovable. Gills 4. Praecaudal vertebrae with very feeble parapophyses and no epipleurals. No spinous dorsal fin. Clavicles, coracoids, and post-clavicles much expanded. No ventral fins. Body encased in a carapace formed of large, juxtaposed, mostly hexagonal bony plates. Vertebrae 14 to 16.

The species of "Trunk-Fishes" number about 20, and are referable to 3 genera: Aracana, Ostracion, Lactophrys; all belong to the tropical seas, living near the bottom in shallow water. The genus Ostracion is represented by one species in the Upper Eocene.

The rigid box in which these fishes are encased entails more use of the dorsal and anal fins for progression than is customary among fishes. According to Brown Goode, "the propelling force is exerted by the dorsal and anal fins, which have a half rotary, sculling motion, resembling that of a screw propeller; the caudal fin acts as a rudder, save when it is needed for unusually rapid swimming, when it is used as in other fishes; the chief function of the broad pectorals seems to be that of forming a current of water through the gills, thus aiding respiration, which would otherwise be difficult on account of the narrowness and inflexibility of the branchial apertures. When taken from the water, one of these fishes will live for two or three hours, all the time solemnly fanning its gills, and when restored to its native element seems none the worse for its experience, except that, on account of the air absorbed, it cannot at once sink to the bottom." "No group of tropical fishes," says the same author, "is so thoroughly worked out in the writings of the fathers of natural history as this one. Over 200 years ago every species of trunk-fish now taken from the Atlantic was known to and described by the naturalists, and it is a well-deserved tribute to their discrimination as zoologists to say that none of the many efforts which have since been made to subdivide their species have been at all successful."

Division II.—GYMNODONTES.

Supraclavicle oblique, sometimes nearly horizontal; lower three pectoral pterygials enlarged and immovably united to the coracoscapular cartilage; upper pterygial small, suturally united to the scapula. Anterior vertebrae with bifid divergent neural spines. Basis cranii simple; suture between dentary and articular evident. Pelvis absent.

The spinous dorsal and the ventral fins are constantly absent, the praemaxillaries are united to the maxillaries, and the teeth are coalescent, forming a beak; parapophyses are not developed, and epipleurals are absent.

Fam. 1. Tetrodontidae.—Beak with a median suture. Interoperculum a long rod, attached to inner face of praeoperculum, sometimes connected with operculum, never with suboperculum. Gills 3. First 4 or 5 praecaudal vertebrae with bifid neural spine and closed neural arch. Skin naked or with movable spines, rarely with bony plates; belly inflatable. Vertebrae 17 to 29.

The "Puffers" or "Globe-Fishes" comprise about 60 species, referable to 5 genera: Tetrodon, Ephippion, Tropidichthys, Xenopterus, Chonerhinus. They inhabit all the tropical and warm seas, a few species being confined to fresh water. Remains of Tetrodon have been found in Upper Eocene and later formations. They are remarkable for the manner in which they inflate themselves with air.^[762] The flesh of most species is poisonous.

Fam. 2. Diodontidae.—Beak without median suture. Interoperculum rod-like, attached posteriorly to the rod-like anterior limb of the suboperculum. Gills 3. All the praecaudal vertebrae with bifid neural spines. Skin with movable spines; belly inflatable. Vertebrae 21 or 22.

Only two genera appear capable of clear definition: Diodon and Lyosphaera; species about 15. Numerous species have been described from the Upper Eocene and later formations.

"Porcupine Fishes" are confined to tropical seas, and have attracted attention from the earliest times, being frequently preserved as "curiosities." Their flesh is regarded as poisonous.

Fam. 3. Molidae.—Beak without median suture. Interoperculum rod-like, attached posteriorly to the rod-like anterior limb of the suboperculum. Gills 4. Anterior praecaudal vertebrae with divergent bifid neural spines and neural canal not roofed in. Body non-inflatable, truncate posteriorly, without caudal peduncle; caudal fin absent, the dorsal and anal fins confluent. Skin rough or tessellated. Vertebrae 17 in Orthagoriscus.

The very young are armed with spines.

The "Sun-Fish" are extraordinary creatures found in the open sea or descending to great depths, and of wide distribution. The number of species is still very uncertain, but two generic forms, Orthagoriscus or Mola and Ranzania, are easily distinguished. Examples of both occur now and then on our coasts. Orthagoriscus mola grows to upwards of 8 feet and to a weight of 1800 pounds. It has been observed to swim slowly about, near the surface, the high dorsal above the water. Its food is said to consist chiefly of jelly-fish and larval fishes; its mode of reproduction and places of breeding are still unknown.

INDEX