Sub-Order 7. Catosteomi.

Air-bladder, if present, without open duct. Parietal bones, if present, separated by the supraoccipital. Pectoral arch suspended from the skull; no mesocoracoid arch; coracoid usually very large. Ventral fins, if present, abdominal, or pelvis attached to the coracoid bones.

The mouth is small and bordered by the praemaxillaries or by the praemaxillaries and a small portion of the maxillaries. The air-bladder is present, except in the Solenostomidae and Pegasidae.

Following the suggestions of Kner and Steindachner and Cope to their logical conclusion, A. S. Woodward, in his valuable catalogue of the Fossil Fishes in the British Museum, has united the Lophobranchs of Cuvier with the Hemibranchs of Cope, a course which seems fully justified, and has received further support from the recent investigations of Swinnerton,^[698] who has proposed to unite the two groups under the new name of Thoracostei. The name Phthinobranchii has also been suggested by O. P. Hay for the same association. The structure of the Lophobranchs (Solenostomidae and Syngnathidae) shows that these fishes are only extremely specialised forms of the group of which the Sticklebacks are the well-known type, and the character of the "tufted" gills alone is surely not of sufficiently great importance to warrant the retention of the Lophobranchii as a division equivalent to the sub-orders adopted in the present classification. Besides, as recently pointed out by A. Huot,^[699] there is no fundamental difference, but only one of degree, between the so-called tufted gill and the normal type; each "tuft" corresponds to one branchial lamella, and at a certain stage of development the disposition of the branchial lamella is the same in a Syngnathus and in an ordinary Teleostean. I have recently attempted to show^[700] that the Lamprididae are related to the Hemibranchii, although sufficiently distinct to warrant the establishment of a division, named Selenichthyes.^[701]

SYNOPSIS OF THE FAMILIES.

Fam. 1. Lamprididae.—Body short and deep, with minute scales. Snout short; mouth toothless, bordered by the praemaxillaries and, to a small extent, by the maxillaries; opercular bones well developed. Gills four, pectinated; branchial apparatus fully developed. Post-temporal bone forked. Vertebrae very numerous (21 + 25), without transverse processes; ribs strong, long. Fins without spines; dorsal and anal elongate. Pectoral fins with very short pterygials folding downwards against the body. Pelvic bones connected with the coracoids, which are very large, and do not form a suture at their ventral extremity. Ventral fins with 15 to 17 rays.

The Opah or King-Fish (Lampris luna), the sole representative of this family, is remarkable for its large size (growing to a length of four feet) and its vivid colours. Its flesh is rich, and intermediate between that of the Salmon and that of the Tunny. It is a pelagic fish of wide distribution, known from the North Atlantic and Mediterranean and from distant points in the Pacific; specimens are occasionally captured on our coasts. It feeds on other fish, but little is known of its habits and nothing of its development.

The affinities of the Lamprididae are very doubtful. Lampris has usually been placed with the Acanthopterygians, a view which is still upheld by Gill.^[702] I now agree with this high authority in regarding the bone which I took for an infraclavicle as a much developed coracoid, and the bone termed by me the coracoid as a pterygial. But it has also been shown, by Starks, that such a thing as an infraclavicle does not exist in the Stickleback, the bone so-called being only a part of the coracoid; and as in most of the Sticklebacks the pelvic bones join the latter, the resemblance between them and Lampris remains. As I have previously pointed out, the absence of spines in the fins, and the position of the ventral fins, together with the great number of rays in the latter, which is only met with in the lower Teleosteans, are characters which necessitate the removal of Lampris from the Acanthopterygians, and I cannot find a better place for them than near the Gastrosteidae.

The whole question of the arrangement of the Physoclists with abdominal ventrals (Catosteomi and Percesoces) is, I feel, much in need of revision, and it may be found advisable to break up this group into a greater number of sub-orders, in which case the Selenichthyes would stand by themselves; the Hemibranchii and Lophobranchii would be united under the former name, as proposed by Woodward, or under that of Thoracostei (Swinnerton) or Phthinobranchii (Hay). The position in the system of the Pegasidae is still somewhat doubtful. This family is regarded by some authors as related to the mail-cheeked Acanthopterygians.

Fam. 2. Gastrosteidae.—Body more or less elongate, naked or protected by bony shields, tapering to a slender caudal peduncle. Head moderate, with short or elongate and tubiform snout; mouth small, terminal, toothed; opercular bones well developed; suborbitals in contact with praeoperculum, protecting the cheek. Gills four, pectinated. Praecaudal vertebrae with strong transverse processes and slender, free ribs. Spinous dorsal represented by isolated spines. Pectoral fins with short pterygials. Pelvic bones usually connected with scapular arch. Ventral fins with one spine and one or two soft rays.

Four genera: Gastrosteus, Apeltes, Eucalia, Spinachia.

The little Three-spined and Two-spined Sticklebacks (Gastrosteus aculeatus and G. pungitius), which include many varieties that have been regarded as distinct species, are among the best known of our British Fishes. They are remarkable for the perfect indifference with which they can be transported from fresh into salt water, and vice versa, and for the elaborate nests which the males build in fresh or brackish water, and over which they watch with the greatest vigilance after the female has deposited her relatively large eggs.^[703] These nests are made of weeds and twigs fastened together by threads secreted by the kidneys of the male. The larger fifteen-spined Stickleback (Spinachia vulgaris) is entirely marine; its nests are to be found on our coasts in sheltered rock-pools, and they are made chiefly of sea-weeds and Hydrozoa. Sticklebacks are short-lived, and are believed to breed only once.

The Gastrosteidae are restricted to the northern hemisphere, being more abundant in the higher latitudes, extending to Iceland, Greenland, and Bering Straits; the southernmost points of their distribution are Algeria in the Old World, and Lower California in the New.^[704]

A very large number of species have been described, but probably only about a dozen deserve to stand.

Fam. 3. Aulorhynchidae.—The genera Aulorhynchus and Auliscus, each with one species from the Northern Pacific, much resemble Spinachia in outward form and in the equal size of the anterior vertebrae, but the snout is still more produced, tubiform, and the ventral fins are formed of one spine and four soft rays. The difference which justifies their separation as a distinct family resides in the disposition of the ribs, which are flattened and ankylosed to the lateral bony shields.

Fam. 4. Protosyngnathidae.—This family appears to be intermediate between the Gastrosteidae and the Aulostomatidae, agreeing with the former in possessing slender, free ribs, with the latter in having the first vertebrae elongate, though to a less degree than in Aulostoma. Its only representative is Protosyngnathus sumatrensis, from a Tertiary freshwater formation in Sumatra, which has been referred, without adequate grounds, to Aulorhynchus or Auliscops.^[705]

Fam. 5. Aulostomatidae.—Allied to the Aulorhynchidae, differing in the ventral fins devoid of spines, formed of 5 or 6 rays, widely removed from the pectoral arch, the very elongate, saddle-shaped anterior vertebra formed by the fusion of several, the large supratemporals produced backward over the anterior vertebra, the very elongate pterygials of the pectoral fin, and the compressed body covered with small ctenoid scales. Ribs are rudimentary or absent. No suborbitals. The snout is long, tubiform; the small terminal mouth bears bands of minute teeth, and the lower jaw has a small barbel at the symphysis. A single genus, Aulostoma, with two species from the Atlantic coasts of tropical America, and two from the Eocene and Miocene of Europe. A. coloratum grows to a length of 26 inches.

Fam. 6. Fistulariidae.—Body greatly elongate, naked. First vertebra much elongate, formed by the fusion of several; strong transverse processes to the ribs in front and behind, those of two vertebrae suturally united; ribs rudimentary or absent. Supratemporal much produced posteriorly, extending over the anterior vertebrae; suborbitals absent; snout forming a long tube, which terminates in a narrow mouth with minute teeth. Spinous dorsal entirely absent. Pterygials of pectoral fin very elongate. Ventral fins very small, with 6 soft rays, inserted far behind the pectoral girdle.

The Flute-mouths, Fistularia, which Dr. Günther describes as "gigantic marine Sticklebacks living near the shore, from which they are frequently driven into the open sea," are represented by three species, from the tropical and subtropical parts of the Atlantic and Indo-Pacific. The middle rays of the forked caudal fin are produced into a long filament. The largest species, F. tabaccaria, reaches a length of 6 feet. The same genus is represented by two species in the Upper Eocene and Oligocene of Europe, and Urosphen, from the Upper Eocene, is regarded as allied to it.

Fam. 7. Centriscidae.—Body moderately elongate, partially enclosed in a bony armour, which is distinct from the endoskeleton. Anterior vertebrae elongate, with strong parapophyses ankylosed to the exoskeleton; no ribs. Suborbitals absent; snout forming a long tube, with small, terminal, toothless mouth. Two dorsal fins, the anterior with a very strong spine. Pterygials of pectoral fin very small. Ventral fins small, with 4 or 5 rays, the pelvic bones in contact with the postclavicles.

Centriscus, with five species in the Atlantic and Pacific Oceans, represents this family at the present day. C. scolopax has occasionally been found on the English coast. Isolated spines from the Pliocene of Tuscany have been referred to the same genus. Rhamphosus, from the Eocene of Monte Bolca, is believed to have been allied to Centriscus.

Fam. 8. Amphisilidae.—Near the preceding, but body extremely compressed and completely enclosed in a thin bony armour which is fused with the endoskeleton; the caudal region, much abbreviated, is free and relegated to the ventral surface, the body terminating in the two dorsals, of which the first bears a strong spine. The ventral fins are far back, very small, formed of 3 or 4 rays.

Amphisile is represented by three or four recent species in the Indian and Pacific Oceans, and two are known from Upper Eocene and Oligocene beds in Europe. Dr. Arthur Willey has observed these fishes in the Southern Pacific. A. strigata "lives in small shoals of about half-a-dozen individuals, and swims about with rapidity in a vertical position, cleaving the water with its razor-shaped body."

Fam. 9. Solenostomidae.—Body moderately elongate, with large star-like ossifications. Anterior vertebrae elongate, without transverse processes; no ribs. Snout much produced, tubiform; mouth, small, terminal, toothless; no praeoperculum; symplectic elongate; gill-opening wide; gill-lamellae small rounded lobes. Two short dorsal fins, the rays of the anterior not articulated, flexible spines. Pterygials of pectoral fin very small. Ventral fins large, with 7 rays, behind the pectoral arch. No air-bladder.

The unique genus, Solenostomus, with three or four species from the Indian and Pacific Oceans, may be regarded as in many respects intermediate between the Centriscidae and the Syngnathidae. In the female the inner side of the ventral fins coalesces with the integuments of the body, forming a large pouch for the reception of the eggs.

Solenorhynchus, from the Upper Eocene of North Italy, probably belongs to this family, but its form is much more elongate, and the exoskeleton is in regular rings.

Fam. 10. Syngnathidae.—Body more or less elongate, protected by an exoskeleton forming rings. Anterior vertebrae not elongate; parapophyses strong, ankylosed to the exoskeleton; no ribs. Snout much produced, tubiform; mouth small, terminal, toothless; no praeoperculum; symplectic elongate; gill-cleft reduced to a very small opening near the upper posterior angle of the gill-cover; gill-lamellae small rounded lobes. A single dorsal fin. Pectoral fins, if present, with very small pterygials; ventrals absent. Caudal fin often absent; tail sometimes prehensile.

This family embraces about 175 marine species, and is represented over the greater part of the world. Principal genera: Siphonostoma, Syngnathus, Penetopteryx, Ichthyocampus, Nannocampus, Osphyolax, Urocampus, Doryichthys, Coelonotus, Stigmatophorus, Nerophis, Protocampus, Gastrotoceus, Solenognathus, Hippocampus, Acentronura, Phyllopteryx.

Remains are found in the Upper Eocene and Miocene beds of Europe, and have been referred to Siphonostoma and Syngnathus, and to the extinct genus Calamostoma. It is probable that Pseudosyngnathus, from the Upper Eocene of Monte Bolca, is the type of a distinct family.

The best known members of this family are the Needle-Fish or Pipe-Fish (Siphonostoma and Syngnathus) and Sea-Horse (Hippocampus) of our coasts. The latter, like Amphisile, swims with the body in a vertical position. In most species the male takes charge of the eggs, in a pouch under the tail (Siphonostoma, Syngnathus, Penetopteryx, Nannocampus, Stigmatophorus, Hippocampus), in a groove under the tail (Phyllopteryx), or in a groove on the abdomen (Doryichthys, Coelonotus, Nerophis, Gastrotoceus).

An Australian species of Syngnathus has been described by E. P. Ramsay under the name of S. intestinalis, from its living inside Holothurians, in the manner of Fierasfer, and G. Lunel has observed a Doryichthys to offer a similar instance of inquilinism.

One of the most remarkable types of Syngnathids is Phyllopteryx, from Australia. The spines and knobs of the head and body are furnished with dermal appendages, which closely imitate the fucus among which they live.

Fam. 11. Pegasidae.—Body short or moderately elongate, encased in an exoskeleton forming rings. Anterior vertebrae not elongate; no ribs. Snout produced beyond the mouth, which is small, inferior, and toothless; no praeoperculum, no symplectic; gill-opening very small; gills pectinated. A single dorsal fin. Pectoral fins large, horizontal; ventrals reduced to one or two filamentous rays, behind the scapular arch. Air-bladder absent.

Five or six species, referable to two genera, Pegasus and Parapegasus, make up this family. They are very small fishes, inhabiting the coasts of China, Japan, Arabia, the Malay Archipelago, and Australia. Pegasus is remarkable among all fishes in having the five anterior rays of the pectoral fin transformed into strong spines.

Sub-Order 8. Percesoces.

Air-bladder, if present, without open duct. Parietal bones separated by the supraoccipitaL Pectoral arch suspended from the skull; no mesocoracoid arch. Ventral fins, if present, abdominal, or at least with the pelvic bones not solidly attached to the clavicular arch.

This group connects the Haplomi with the Acanthopterygii, the Scombresocidae being somewhat related to the Cyprinodonts,^[706] whilst the Anabantidae show distinct affinity to the Osphromenidae in the following sub-order. Other families, previously included among the Scombriform Acanthopterygians, are placed here on the assumption that the loose attachment of the pelvic bones to the clavicles is a primitive character, and not the result of degeneration, such as occurs in some cases among true Acanthopterygians. Although this sub-order is perhaps only an artificial association, it must be borne in mind that, notwithstanding the very wide divergence which exists between the first and last families, and however dissimilar their members may appear to be at first sight, a gradual passage may be traced connecting the most aberrant types.

Synopsis of the Families.

Fam. 1. Scombresocidae.—Maxillary entering the border of the upper jaw; dentition moderately strong or feeble. Lower pharyngeal bones united. Praecaudal vertebrae with strong parapophyses supporting the ribs. Body covered with cycloid scales. Pectoral fins inserted very high up; ventral fins widely separated from the pectorals, without spines, with 6 rays. Dorsal fin opposed to the anal, and likewise formed entirely of soft rays. Air-bladder generally present, sometimes cellular.

The shape of the head and body vary greatly, and the pectoral fin may reach an extraordinary wing-like development. The dorsal fin may be followed by a series of finlets, as in many of the Scombridae. Most of the Scombresocidae, of which about 200 species are known, are marine; some are carnivorous, others (Hemirhamphus) mainly herbivorous, feeding on green algae. Nearly all are in the habit of making great leaps out of the water, this tendency culminating in the Flying-Fish (Exocoetus), which skip or sail through the air in a manner the explanation of which has given rise to much controversy. According to the latest evidence^[707] the sole source of motive power is the action of the strong tail while in the water; no force is acquired while the fish is in the air. The pectorals are not used as wings but as parachutes. There is every passage between the small pectoral fin of a Saurie (Scombresox) or a Hemirhamphus and the swallow-like wings of the most developed Exocoetus. The genus Hemiexocoetus is a very remarkable connecting form. The Gar-Pike (Belone), of which one species is common on our coasts, have both jaws produced into a long slender beak; the bones are green. In Hemirhamphus the lower jaw only is prolonged; some of the species, living in fresh water, are viviparous, the anal fin being modified into a copulatory organ, as in many Cyprinodonts.

Scombresocidae occur in all the tropical and temperate seas. Belone, Scombresox, and Hemirhamphus are found in Upper Eocene and Miocene beds of Europe, and, as stated above, Protaulopsis should perhaps be referred to this family.

Fam. 2. Ammodytidae.—Maxillary excluded from the border of the upper jaw; mouth protractile; dentition feeble or absent. Lower pharyngeal bones separate. Praecaudal vertebrae without parapophyses. Body covered with very small cycloid scales. Pectoral fins nearer the ventral than the dorsal line; ventral fins, if present, widely separated from the pectorals, without spine, with 6 rays. Dorsal and anal fins more or less elongate, formed of soft rays. Air-bladder absent.

The existing genera, Ammodytes, with 8 species, from the temperate coasts of the northern hemisphere, and Hypoptychus, from northern Japan, with a single species, are deprived of ventral fins, and their exact relations remained obscure until the structure of the Oligocene Cobitopsis revealed their affinity to the Scombresocidae, or at least their pertinence to the present suborder. The Greater Sand-Eel or Launce (Ammodytes lanceolatus) and the Lesser Sand-Eel (A. tobianus) are common on our coasts, and are remarkable for the manner in which, by means of their sharp-pointed snout, they bury themselves with great rapidity in the sand, darting in and out like arrows.

Fam. 3. Atherinidae.—Maxillary excluded from the border of the upper jaw; dentition more or less developed. Body covered with cycloid or ctenoid scales. Ribs attached to strong parapophyses. Pectoral fins inserted high up; ventral fins more or less approximated to the pectorals, with one spine and five soft rays; pelvic bones connected with the clavicular symphysis by a ligament. Two well-separated dorsal fins, the anterior small and formed, at least in part, of spinous rays. Air-bladder present.

Carnivorous Fishes, mostly marine and of small size, much valued as food, and distributed along the coasts of most tropical and temperate seas; some inhabit fresh waters. A silvery lateral band, or "stole," is usually present. About 65 species are known, referred to 14 genera: Atherina, Iso, Chirostoma, Thyrina, Atherinella, Labidesthes, Atherinopsis, Atherinops, Telmatherina, Neatherina, Pseudomugil, Rhombatractus, Aida, Melanotaenia.

Represented in the Upper Eocene of Europe by several species of Atherina and by the extinct genus Rhamphognathus.

Fam. 4. Mugilidae.—Maxillary excluded from the border of the upper jaw; dentition feeble or absent. Body covered with cycloid scales. Ribs attached to the extremity of strong parapophyses. Pectoral fins inserted high up; ventral fins more or less approximated to the pectorals, with one spine and five soft rays; pelvic bones suspended from the post-clavicles. Two well-separated dorsal fins, the anterior formed of a small number of spines. Air-bladder present.

These Fishes are closely related to the preceding, of which they are a further specialisation, the pharyngeal bones having a complicated structure, much reducing the oesophageal opening, and the vertebrae being reduced in number (24 to 26 instead of 32 to 60). They feed on organic matter contained in mud, and inhabit the fresh waters and coasts of the temperate and tropical regions. The species number about 100. Principal genera: Mugil, Myxus, Anostomus, Joturus. Grey Mullets (Mugil) are represented on our coasts by three species, valued as food, one of which (M. capito) has a remarkably wide range, occurring from Scandinavia to the Cape of Good Hope. Remains referred to the same genus occur in the Miocene and Oligocene.

Fam. 5. Polynemidae.—Maxillary excluded from the border of the upper jaw; dentition feeble. Body covered with ctenoid scales. Ribs attached to the extremity of strong parapophyses. Pectoral fin inserted low down, with a lower portion consisting of free rays; the upper portion, or fin proper, attached to the scapula, the lower to a fenestrate bone which appears to be formed by coalesced pterygials (Fig. 391, pt.). Ventral fin more or less approximated to the pectoral, with one spine and five soft rays; pelvic bones suspended from the post-clavicles. Two well-separated dorsal fins, the anterior formed of a small number of spines. Air-bladder, if present, very large.

The vertebrae number 24 (10 + 14).

Three closely allied genera: Polynemus, Pentanemus, and Galeoides, with about 25 species, from the shores of tropical seas, often entering rivers. Some attain a length of 4 feet, and are valued as food or for the isinglass yielded by their air-bladder. The free pectoral filaments are organs of touch, and can be moved independently of the fins.

Fam. 6. Chiasmodontidae.—The deep-sea genera, Chiasmodon, Pseudoscopelus, and Champsodon, which have been placed either with the Gadidae, the Trachinidae, or the Berycidae, may be referred to the Percesoces, as the pelvic fins have only a ligamentous connexion with the pectoral arch. Unfortunately, the skeleton has only been examined in Champsodon; it is remarkably similar to that of the Atherinidae. As in Atherinichthys, the posterior extremity of the air-bladder is protected by a bony sheath formed by the expanded ring-like haemal processes of the anterior caudal vertebrae. Vertebrae 32 (16 + 16). The scales are absent or very small and spinulose, the mouth large, with cardiform teeth; spinous dorsal short, soft dorsal and anal elongate. Chiasmodon and Pseudoscopelus have a complicated system of sensory organs on the body, which in the latter suggest the photophores of Scopelids. Champsodon vorax is a fish of extreme voracity, swallowing prey much larger than itself. Only four species of this family are known.

Fam. 7. Sphyraenidae.—Maxillary excluded from the border of the upper jaw; dentition very strong. Body covered with cycloid scales. Anterior ribs sessile, the rest inserted on parapophyses. Pectoral fin nearer the ventral than the dorsal outline; ventral fin more or less approximated to the pectoral, with 1 spine and 5 soft rays; pelvis not connected with the pectoral arch. Two well-separated dorsal fins, the anterior formed of a small number of spines. Air-bladder large. Vertebrae 24.

Carnivorous Pike-like Marine Fishes from the tropical and sub-tropical seas, often found at the mouths of rivers. The "Barracudas" form a single genus, Sphyraena, with about 20 species, the largest of which grow to 8 feet and are dangerous to people bathing; many are valued as food, but some are reported to be poisonous, at least at certain seasons. Remains of several species are known from the Eocene and later periods in Europe and North America.

Fam. 8. Tetragonuridae.—Maxillary excluded from the border of the upper jaw; dentition feeble. Oesophagus with lateral sacs which are beset with papillae internally; a series of gill-raker-like knobs below the pseudobranchiae. Body covered with rhomboidal, striated scales in oblique transverse series, those of every single transverse series coherent. Ribs mostly sessile. Pectoral fin nearer the ventral than the dorsal outline. Ventral fin with 1 spine and 5 soft rays, near the pectoral, but pelvis free from the pectoral arch. A long continuous dorsal fin, its anterior portion formed of numerous short spines. Air-bladder absent. Vertebrae 58.

This family includes a single, rather rare fish, Tetragonurus cuvieri, from the Mediterranean and neighbouring parts of the Atlantic and the South Pacific. It is said to descend to great depths at certain seasons, and to feed on Medusae; its flesh is poisonous. Young specimens have been observed by Emery to live in the respiratory cavity of large Salpae.

Fam. 9. Stromateidae.—Although including a number of forms very unlike Tetragonurus in external appearance, there is no doubt that this family, hitherto placed near the Scombridae, is very closely allied to the preceding, agreeing with it in the presence of lateral oesophageal sacs bearing internally papillae (which are besides beset with setiform teeth), and, in most genera, in the presence of a series of knobs, more or less similar to gill-rakers, below the pseudobranchiae. The pelvic bones are sometimes free from the pectoral arch, as in the Tetragonuridae, sometimes more closely attached, but only by ligament, and movable. The principal difference resides in the scales, which are always cycloid and usually very small and more or less deciduous, and in the spinous dorsal being shorter than the soft, or even quite rudimentary. The ventrals are sometimes absent. The air-bladder is present or absent. The number of vertebrae varies from 24 to 46.

Marine Fishes, pelagic or deep-sea, feeding on Crustaceans, Medusae, or the fry of other fish. About 45 species are known, referable to 10 genera: Nomeus, Cubiceps, Psenes, Seriolella, Psenopsis, Centrolophus, Lirus, Stromateus, Peprilus, and Stromateoides. Many of the species have a wide distribution, but are rare in collections.^[708] The Black-Fish (Centrolophus niger) and its close ally C. britannicus, and the Rudder-Fish (Lirus perciformis and L. medusophagus), have occurred, at rare intervals, on the British coasts. The Stromateidae were represented by several species in the Cretaceous (Platycormus and Homosoma).

The widely distributed Nomeus gronovii, so remarkable for its enormous ventral fins, folding in a ventral groove, has been observed in New South Wales to be only found on the coast when the Siphonophores called "Portuguese Men-of-War" or Physalia are driven ashore, the fish swimming beneath them, as the young Caranx are in the habit of doing under Medusae. As observed by Waite,^[709] the benefit of such a partnership must primarily be with the fish, for it is a voluntary agent, whereas the Physalia has no power of locomotion. "If the fish secures safety from its enemies by entering the area embraced by the deadly tentacles of the Physalia, which attain a length of 10 to 12 feet, it must be immune to their influence: a remarkable condition, considering that small fish have often been seen in their stomachs and entangled in their tentacles." This observer adds: "It is probable that, in addition to protection, the fish derives its food from association with the Physalia, much as does the Remora in accompanying a shark. The Physalia doubtless paralyses many more animals than it can consume—the residue falling to the lot of the fishes, which may be present to the number of ten."

Fam. 10. Icosteidae.—The so-called "Rag-Fishes," in which the skeleton is quite soft and cartilaginous, are aberrant deep-sea forms evidently related to the Stromateidae; they lack the oesophageal teeth and the processes of the last gill-arch, but Icosteus at least has the gill-raker-like knobs below the pseudobranchiae. The pelvis is widely separated from the clavicles. Spines are absent in the fins, and the body is naked or covered with small cycloid scales. Vertebrae in large number (up to 70).

Icosteus, Icichthys, and Acrotus, each with a single species, from the Pacific coast of North America.

Fam. 11. Ophiocephalidae.—Maxillary excluded from the border of the upper jaw. Head and body covered with cycloid scales. Anterior ribs sessile, the remainder inserted on the parapophyses. Pectoral fin low down; ventral fin, if present, near the pectoral, with 6 soft rays; pelvic bones connected with the clavicular symphysis by ligament. Dorsal and anal fins long, without spines. Air-bladder present, much elongate.

These Fishes are provided with an accessory superbranchial cavity, and are able to breathe atmospheric air. All are inhabitants of fresh waters and are carnivorous. Only two genera are known: Ophiocephalus, with about 25 species from Eastern Asia and 3 from Tropical Africa, and Channa, distinguished by the absence of ventral fins, with 3 species from Ceylon and China.

Fam. 12. Anabantidae.—Differ from the preceding, to which they are closely related, in having part of the dorsal and anal fins and the outer ventral ray spinous, and a shorter, Perch-like body covered with ctenoid scales. The accessory superbranchial organ is still more developed, with thin bony laminae, which are more or less folded and covered with a mucous membrane. These Fishes can live a long time out of water, and the name Anabas scandens, or Climbing Perch, recalls the fact that its first observers in India ascribed to it the habit of climbing up low trees by means of the spines with which its gill-covers and ventral fins are armed. This species, which attains a length of 8 inches, is found in estuaries and fresh waters of India, Ceylon, Burma, and the Malay Peninsula and Archipelago; 3 other species occur in the Malay Archipelago, and 11 in Africa.

Sub-Order 9. Anacanthini.

Air-bladder without open duct. Parietal bones separated by the supraoccipital; prootic and exoccipital separated by the enlarged opisthotic. Pectoral arch suspended from the skull; no mesocoracoid arch. Ventral fins below or in front of the pectorals, the pelvic bones posterior to the clavicular symphysis and only loosely attached to it by ligament.

Fins without spines; caudal, if present, without expanded hypural, perfectly symmetrical, and supported by the neural and haemal spines of the posterior vertebrae and by basal bones similar to those supporting the dorsal and anal rays. This type of caudal fin must be regarded, as I have pointed out,^[710] as secondary, the Gadidae being, no doubt, derived from Fishes like the Macruridae, in which the homocercal fin had been lost. The scapular foramen or fenestra is nearly always between the scapular and coracoid bones, as in the Trachinidae and several allied families, not in the coracoid, as in the other Acanthopterygians. The first two vertebrae have no epipleurals.

Mr. C. Tate Regan,^[711] who has recently given a good definition of the Anacanthini, divides them into three families.