ORDER IV  .—TELEOSTEI Paired fins non-lobate, the ventrals without baseosts . Mandible suspended from the upper segment of the hyoid arch . Splenial bone absent . Supraoccipital bone present . Heart without muscular conus arteriosus, or with much reduced conus, with one, exceptionally two, rows of valves . Air-bladder, if present, communicating with the dorsal side of the oesophagus or digestive tract, or completely closed . SUB-ORDER I.--MALACOPTERYGII Air bladder, if, present, with a duct . Opercle well developed . Pectoral arch suspended from the skull; mesocoracoid bone present . Fine without spines, the ventrals abdominal (rarely absent) . Anterior vertebrae distinct, without Weberian ossicles . Families: Pholidophoridae, Archaeomenidae, Oligopleuridae, Leptolepidae, Elopidae, Albulidae, Mormyridae, Hyodontidae, Notopteridae, Osteoglossidae, Pantodontidae, Ctenothrissidae, Phractolaemidae, Saurodontidae, Chirocentridae, Clupeidae, Chanidae, Salmonidae, Alepocephalidae, Stomiatidae, Gonorhynchidae, Cromeriidae .

Unquestionably the most generalized sub-order, having most incommon with the Holostean ganoids . The first four families, of Triassic to Cretaceous

age, are so closely connected with these Ganoids that their allocation to the Teleosteans must be regarded as provisional . Some of the Pholidophoridae were flying fishes . The Elopidae and Albulidae are also low forms, traced back to the Cretaceous seas, having points in common with the Ganoids (gular plate in the former, conus arteriosus with two rows of valves in the latter) . The Mormyridae are among the most extraordinary fishes, and, like the four families which follow in the above list, confined to fresh waters . Other families, like the Chirocentridae, Clupeidae and Salmonidae, are entirely or partly marine, the two last being of great economic importance . The Alepocephalidae and Stomiatidae are restricted to the deep sea . See ANCHOVY, HERRING, MENHADEN, MORMYR, PILCHARD, SALMONIDAE, SHAD and SPRAT . SUB-ORDER II.—OSTARIOPHYSI Air-bladder, if well developed, with a duct . Pectoral arch suspended from the skull; mesocoracoid bone present . Fins without spines, or dorsal and pectoral with a single spine formed by the co-ossification of the segments of an articulated ray . The anterior four vertebrae strongly modified, often co-ossified, and bearing a chain of small bones (so-called Weberian ossicles) connecting the air-bladder with the ear .

Families: Characinidae, Gymnotidae, Cyprinidae, Siluridae, Loricariidae, Aspredinidae . One of the most natural

groups of the class Pisces, as demonstrated by M . Sagemehl in 1885 . The Characinidae are the most generalized, although perhaps not directly derived from the Amiid Ganoids, as believed by Sagemehl; they show great variety of form and dentition, and are confined to Central and South America and Africa . The Gymnotidae, which include the so-called electric eel, are closely related to the Characinidae, and occur only in South America . The largest families are the Cyprinidae and Siluridae . With the exception of a few Siluridae, the Ostariophysi are all fresh-water fishes . SUB-ORDER III.—SYMBRANCH II Eel-shaped fishes without paired fins, with the pectoral arch free or suspended from the skull, without mesocoracoid bone, and with the anterior vertebrae distinct, without Weberian ossicles . Gill-openings confluent into a single, ventral slit . Air-bladder absent . Families: Symbranchidae and Amphipnoidae . Like the Apodes, which they resemble in general appearance, these fishes are no doubt derived from some low type with abdominal ventral fins, but whether from the Malacopterygii or the Haplomi we have as yet no data from which to conclude .

Inhabitants of the fresh or brackish waters of south-eastern

Asia, tropical America, Australia and Tasmania . In the cuchia, Amphipnous cuchia, the gills are much reduced, and a respiratory air-sac extends on each side of the body behind the head, communicating with the gill-cavity . - SUB-ORDER IV.—APODES Air-bladder, if present, with a duct . Praemaxillary bones absent; the maxillaries, if present, separated on the median line in front by the coalescent ethmoid and vomer . Pectoral arch, if present, not connected with and remote from the skull; mesocoracoid bone absent .. Fins without spines, the ventrals absent . Anterior vertebrae distinct, without Weberian ossicles . Elongate, serpentiform fishes with naked skin, or with minute scales imbedded in the skin . Families: Anguillidae, Nemichthyidae, Synaphobranchidae, Saccopharyngidae, Muraenidae . A large group of aberrant, degraded fishes, heralded by the Cretaceous genus Urenchelys, the most generalized of eels . Mostly marine, many bathybial; some living principally in fresh water, but breeding in the sea, like the common eel (see articles EEL and MURAENA) . SUB-ORDER V.—HAPLOMI Air-bladder, if present, with a duct .

Opercle well developed . Pectoral arch suspended from the skull; no mesocoracoid bone . Fins usually without, rarely with a few spines; ventrals abdominal, if present . Anterior vertebrae distinct, without Weberian ossicles . Families: Galaxiidae, Haplochitonidae, Enchodontidae, Esocidae, Dalliidae, Scopelidae, Alepidosauridae, Cetomimidae, Chirothricidae, Kneriidae, Cyprinodontidae, Amblyopsidae, Stephanoberycidae, Percopsidae . The

absence of the mesocoracoid bone distinguishes these fishes from the Malacopterygii, and the presence of a duct to the air-bladder separates them from the Percesoces, to some of which, the Scombresocidae and the Atherinidae, they are linked by the Cyprinodontidae; whilst the Scopelidae are connected with the Berycidae by the Stephanoberycidae . The type family of this sub-order is that of the Esocidae or pike, inhabitants of the fresh waters of Europe, northern Asia, and North America . The Galaxiidae are mostly fresh-water fishes and have a wide distribution in the southern hemisphere (southern parts of South America, New Zealand, South Australia and Tasmania, Cape of Good Hope), one species being identical in South America, the Falkland Islands, New Zealand and Tasmania . Their distribution has been regarded as affording support to the theory of an Antarctic continent in Tertiary times . However, several of the species spend part of their life, and even breed, in the sea, whilst others may be regarded as having become more recently adapted to fresh water, so that the argument derived from their range is not so strong as if we had to deal with exclusively fresh-water fishes . The Cyprinodontidae are partly brackish, partly fresh-water fishes, whilst the Scopelidae, which are traced back to the Chalk, are all marine, many being inhabitants of great depths . SUB-ORDER VI.—HETEROMI Air-bladder without duct .

Opercle well developed, parietal bones separating the frontals from the supraoccipital . Pectoral arch suspended from the supraoccipital or the epiotic, the

post-temporal small and simple or replaced by a ligament; no mesocoracoid bone . Ventral fins abdominal, if present . Families: Dercetidae, Halosauridae, Lipogenyidae, Notacanthidae, Fierasferidae . Closely related to the Haplomi, but separated chiefly on account of the closed air-bladder . Mostly deep-sea fishes, some of which appeared as early as the Cretaceous period . The genus Fierasfer comprises small degraded fishes commensals of Holothurians and bivalve molluscs . SUB-ORDER VII.—SELENICHTHYES Air-bladder without duct . Opercle well developed . Pectoral arch suspended from the skull; no mesocoracoid bone . Fins with-out spines . Ventral fins abdominal, with very numerous (15 to 17) rays .

A very aberrant type, of uncertain

affinities . Its only representative is the opah, Lampris luna, a large pelagic fish of wide distribution . SUB-ORDER VIII.—THORACOSTEI Embracing the Hemibranchii and Lophobranchii, but excluding the Hypostomides (Pegasidae), which the investigations of F . E . Jungersen show to be aberrant mail-cheeked Acanthopterygians . , Air-bladder without duct . Pectoral arch suspended from the skull: no mesocoracoid bone . Ventral fins abdominal, if present . Branchial arches more or less reduced . Families: Gastrosteidae, Aulorhynchidae, Protosyngnathidae, Aulostomatidae, Fistulariidae, Centriscidae, Amphisilidae, Solenostomidae, Syngnathidae . The two latter families institute the division Lophobranchii, in which the gill-lamellae are enlarged and 'orm rounded lobes . See articles SEA-HORSE, STICKLEBACK, and PIPE-FISHES .

SUB-ORDER IX.—PERCESOCES Air-bladder, if present, without duct . Parietal bones separated by the supraoccipital . Pectoral arch suspended from the skull; no mesocoracoid bone . Ventral fins, if present, abdominal, or at least with the pelvic bones not solidly attached to the clavicular arch . Families: Scombresocidae, Ammodytidae, Atherinidae, Mugilidae, Polynemidae, Chiasmodontidae, Sphyraenidae, Tetragonuridae, Stromateidae, Icosteidae, Ophiocephalidae, Anabantidae . This

series of families connects the Haplomi with the Acanthopterygii . The Percesoces are mostly marine, but the two last families are exclusively fresh-water . Some are inhabitants of great depths, others are pelagic, like the flying-fish (Exocoetus) . SUB-ORDER X.—ANACANTHINI Air-bladder without duct . Parietal bones separated by the supraoccipital; prootic and exoccipital separated by the enlarged opisthotic . Pectoral arch suspended from the skull; no mesocoracoid bone . 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 . Families: Macruridae, Gadidae, Muraenolepididae . Nearly all marine . The Macruridae are among the most characteristic fishes of the great depths . The Gadidae include some of the most valuable

food-fishes . SUB-ORDER XI.—ACANTHOPTERYGII Air-bladder usually without duct . Opercle well developed ; supraoccipital in contact with the frontals . Pectoral arch suspended from the skull; no mesocoracoid bone . Ventral fins thoracic or jugular, more or less firmly attached to the clavicular arch . Gill-opening usually large, in front of the base of the pectoral fin . The character from which this sub-order, the most comprehensive of the whole class, derives its name, viz., the presence of non- xxvl . 18articulated, spiny rays in the dorsal and anal fins, is by no means universal, exceptions to the rule being numerous .

Division I . Beryciformes.—Families: Berycidae, Monocentridae, Polyymixiidae . the most

primitive of the Acanthopterygians, already well represented in the Chalk . A duct has been observed to be sometimes present between the air-bladder and the digestive tract . All marine, several bathybial . Division II . Perciformes.—Families: Pempheridae, Serranidae, Anomalopidae, Pseudochromididae, Cepolidae, Hoplognathidae, Sillaginidae, Sciaenidae, Scorpididae, Caproidae, Centrarchidae, Cyphosidae, Lobotidae, Toxotidae, Nandidae, Percidae, Acropomatidae, Gerridae, Lactariidae, Trichodontidae, Pristipomatidae, Sparidae, Mullidae, Latrididae, Haplodactylidae, Chaetodontidae, Drepanidae, Osphromenidae, Acanthuridae, Teuthididae, Embiotocidae, Cichlidae, Pomaeentridae, Labridae, Scaridae . The Percidae, Centrarchidae, Toxotidae, Nandidae, Osphromenidae, Embiotocidae, and Cichlidae are fresh-water fishes, the others are all or nearly all marine . Aipichthys, which is included among the Scorpididae, is one of the few Acanthopterygian types known to have existed as early as the Cretaceous period . See articles CICHLIDS, MULLET, MURRAY COD, PARROT-FISHES, PERCH, PIKE-PERCH, SHEEPSHEAD, WRASSE . Division III . Scombriformes.—Families: Carangidae, Rhachicentridae, Scombridae, Trichiuridae, Histiophoridae, Xiphiidae, Luvaridae, Coryphaenidae, Bramidae .

Marine fishes, several being pelagic and among the largest Teleosteans and swiftest swimmers . See articles

HAIR-TAIL, MACKEREL, PILOT-FISH, SWORD-FISH, TUNNY . Division IV . Zeorhombi.—Families: Zeidae, Amphistiidae, Pleuronectidae . Division V . Kurtiformes.—A single family, Kurtidae, with a single genus and species from the Indian and Pacific oceans . Division VI . Gobiiformes.— A single family, Gobiidae . Division VII . Discocephali.— A single family, Echeneididae . The remarkable remoras attach themselves by means of a cephalic disk to boats or to sharks, turtles, cetaceans, and other large swift-swimming animals . They form an isolated group, and have no real affinity with the Scombridae, with which they have long been associated .

Division VIII . Scleroparei.—Families: Scorpaenidae, Hexagrammidae, Comephoridae, Rhamphocottidae, Cottidae, Cyclopteridae, Platycephalidae, Hoplichthyidae, Agonidae, Pegasidae, Triglidae, Dactylopteridae . The " Mail-cheeked " Acanthopterygians include a great variety of forms, mostly living in the sea, the best known being referred to in the articles FLYING-FISH ,CURNA RD, LUMP-SUCKER, and

MILLER'S-THUMB . Division IX . Jugulares.—Families: Trachinidae, Percophiidae, Leptoscopidae, Nototheniidae, Uranoscopidae, Trichodontidae, Callionymidae, Gobiesocidae, Blenniid e, Batrachidae, Pholididae, Zoarcidae, Congrogadidae, Ophidiidae, Podatelidae . Nearly all marine, some deep-sea . Macrius amissus, which probably belongs to the Leptoscopidae, measures 5 ft. and is the largest known deep-sea Teleostean . The other members of this division are mostly small, Anarrhichas being another exception . The weevers (Trachinus) are dangerous stinging fishes . Division X . Taeniosomi.—Families: Trachypteridae, Lophotidae . Deep-sea or pelagic fishes, some attaining a large size .

SUB-ORDER XII.—OPISTHOMI Air-bladder without duct . Opercle well developed, hidden under the skin; supraoccipital in contact with the frontals . Pectoral arch suspended from the vertebral

column, far behind the skull; no mesocoracoid bone . Vertical fins with spines . Ventral fins absent . Eel-shaped fishes standing in the same relation to the Acanthop- terygii as do the Apodes to the Malacopterygii . The single family, Mastacembelidae, is possibly derived from the Blenniidae . Fresh and brackish waters of southern Asia and tropical Africa . SUB-ORDER XIII.—PEDICULATI Air-bladder without duct . Opercle well developed, hidden under the skin; supraoccipital in contact with the frontals . Pectoral arch suspended from the skull; no mesocoracoid bone . Ventral fins, if present, jugular .

Gill-opening reduced to a foramen situated in or near the axil more or less posterior to the base of the pectoral fin . Body naked or covered with spines or bony tubercles . Connected with the Acanthopterygii Jugulares through the Batrachidae . Families: Lophiidae, Ceratiidae, Antennariidae, Gigantactinidae, Malthidae . Curiously aberrant marine fishes, many bathybial . The best known are the fishing-

frog or angler, Lophius, and the Antennarius, which lives in coral groves or is carried about in mid-ocean among the Sargassum weeds . II SUB-ORDER XIV.--PLECTOGNATHI Air-bladder without duct . Opercular bones more or less reduced; supraoccipital in contact with the frontals; 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 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 . Division I . Sclerodermi.—Families: Triacanthidae, Triodontidae, Balistidae, Ostraciontidae . Division II . Gymnodontes.—Families: Tetrodontidae, Diodontidae, Molidae . The Plectognaths are all marine; the recently discovered Triacanthid Halimochirurgus, remarkable for its long,

tube-like snout, from the Gulf of Manaar, is the only form of this sub-order which is confined to the deep sea . Although so highly specialized, several forms, such as Ostracion (the coffer-fish), Tetrodon and Diodon, were already represented in the upper Eocene . See FILE-FISH, GLOBE-FISH and SUN-FISH . For bibliographical references to the Teleostomi, see ICHTHYOLOGY . (G . A .