694 ICHTHYOLOGY [CLASSIFICATION, apparatus much developed, the gill-openings being generally very wide. Pseudobranchise generally present. Air-bladder more or less simple. Genera : Enyraulis (Anchovies), Coilia, Chatocssus, Clupca (Her ring. Sprat, Shad, Mossbauker, Menhaden, Ale-Wife, Pilchard, Sar dine), Clupeoides, Pellonula, Clupeichlhys, Pellona, Pristigaster, Albula, Elops, Mcgalops, Chanos, Dussumieria, Etrumeus. Several ,of these genera have been found in Tertiary formations ; other fossils are : Tlirissopatcr, Lcptosomus, Opisthopteryx, tfpaniodon, Hahc, Platinx, Ccelogaster, Rliindlus, Scombrochipca, Crossognathus, Spathodactylus, Ghiroccntritcs, and HemitricJias. Family 23. Bathythrisida}. Allied to the hemnsaBathythrissa. Family 24. Chirocentridce. Body covered with thin, deciduous scales ; barbels none. Margin of the upper jaw formed by the interiuaxillaries mesially and by the maxillaries laterally, both bones being firmly united in juxtaposition. Opercular apparatus complete. Adipose tin none : the dorsal fin belongs to the caudal portion of the vertebral column. Stomach with a blind sac ; intes tine short, the mucous membrane forming a spiral fold ; pyloric appendages none. Pseudobranchiae none ; air-bladder incompletely divided into cells ; gill-opening wide. One genus only : Chirocentrus. Family 25. Alepocephalidcv. Body with or without scales ; head naked ; barbels none. Margin of the upper jaw formed by the intermaxillaries and maxillaries, the former being placed along the upper anterior edge of the latter. Opercular apparatus complete. Adipose fin none ; the dorsal fin belongs to the caudal portion of the vertebral column. Stomach curved, without blind sac ; pyloric appendages in moderate number. Pseudobranchiae ; air-bladder absent. Gill-openings very wide. Genera: Alepocephalus, Batky trades, Platytroctcs, and Xcnoderm- ichthys. Family 26. Kotopteridce. Head and body scaly ; barbels none. Margin of the upper jaw formed by the iutennaxillaries mesi;lly and by the maxillaries laterally. Opercular apparatus incomplete. Tail prolonged, tapering. Adipose fin none. Dorsal short, belong ing to the caudal portion of the vertebral column ; anal very long. Stomach without blind sac ; two pyloric appendages. Pseudo- branchise none ; air-bladder present, divided in the interior. The ova fall into the cavity of the abdomen before exclusion. On each side a parieto-mastoid cavity leading into the interior of the skull. One genus only : Notopterus. Family 27. Jfalosauridcc. Body covered with cycloid scales; head scaly ; barbels none. Margin of the upper jaw formed by the intermaxillaries mesially and by the maxillaries laterally. Oper cular apparatus incomplete. Adipose fin none. The short dorsal belongs to the abdominal part of the vertebral column ; anal very long. Stomach with a blind sac ; intestine short ; pyloric appen dages in moderate number. Pseudobranchiaj none. Air-bladder large, simple ; gill-openings wide. Ovaries closed. One genus only : Halosdurus. Family 28. Hoplopleuridce. Body generally with four series of subtriangular scufcs, and with intermediate scale-like smaller ones. One (?) dorsal only ; head long, with the jaws produced. Extinct. Genera : Dercctis, Lcptotrachdus, Pelargorliynchus, Plinthophorus, Saurorhamphus, Eurypholis, Ischyroccphalus. Family 29. Gymnotidce. Headscaleless ; barbels none. Body elon gate, eel-shaped. Margin oftheupper jaw formed in the middle by the intermaxillaries and laterally by the maxillaries. Dorsal fin absent or reduced to an adipose strip ; caudal generally absent, the tail terminating in a point. Anal fin exceedingly long. Ventrals none. Extremity of the tapering tail capable of being reproduced. Vent situated at, or at a short distance behind, the throat. Humeral arch attached to the skull. Ribs well developed. Gill -openings rather narrow. Air-bladder present, double. Stomach with a caecal sac and pyloric appendages. Ovaries with oviducts. Genera : Stcrnarchus, Ramiihichthys, Stcrnopyyus, Carapus, Gymnotus (Electric Eel). Family 30. SymbrancliidcK. Body elongate, naked or covered with minute scales ; barbels none. Margin of the upper jaw formed by the intermaxillaries only, the weft-developed maxillaries lying behind and parallel to them. Paired fins none. Vertical tins rudi mentary, reduced to more or less distinct cutaneous folds. Vent situated at a great distance behind the head. Eibs present. Gill- openings confluent into one slit situated on the ventral surface. Air-bladder none. Stomach without csecal sac or pyloric append ages. Ovaries with oviducts. Genera: Amphipnous, Monoptcnis, Symlranclius, Chilobranchus. Family 31. Murixnidce (Eels). Body elongate, cylindrical or band- shaped, naked or with rudimentary scales. Vent situated at a great distance from the head. Ventral fins none. Vertical fins, if present, confluent, or separated by the projecting tip of the tail. Sides of the upper jaw formed by the tooth bearing maxillaries, the fore part by the intermaxillary, which is more or less coalescent with the vomer and ethmoid. Humeral arch not attached to the skull. Stomach with a blind sac ; no pyloric appendages. Organs vf reproduction without efferent ducts. Genera : Nemichthys, Cyema, Saccopharynx, Synaphobranchus, Anguilla, Conger, Congromurccna, Murcvncsox, Netlastoma, Sauren- chcli/s, Oxyconger, Hoplunnis, Myrus, Myropliis, Paramyrus, Chilo- rhinus, Murcenichthys, Ophichthys, Aloringua, Murccna, Enchelycore. OIUIER V. Lophobranchii. . The gills are not laminated, but composed of small rounded lobes attached to the branchial arches. Gill-cover reduced to a large simple plate. Air-bladder simple, without pneumatic duct. A dermal skeleton, composed of numerous pieces arranged in segments, replaces more or less soft integuments. Muscular system not much developed. Snout prolonged. Mouth terminal, small, toothless, formed as in Acanthopterygians. Family 1. Solcnostomidce. Gill-openings wide. Two dorsal fins, the rays of the anterior not articulated. All the other fins well developed. One genus only : Solcnostoma, which was preceded in the Tertiary epoch by Solenorhynchus (Monte Postale). Family 2. Syngnathidce. Gill-openings reduced to a very small opening near the upper posterior angle of the gill-cover. One soft dorsal fin ; no ventrals, and sometimes one or more of the other fins are also absent. Pipe-Fishes and Seahorses. Fossil remains occur at Monte Bolca, Besides species of Siphonostoma and Syngnathus (Pscudosyngnathus),. remains of an extinct genus, Calamostoma, allied to Hippocampus, but with a distinct caudal fin, have been found. Genera : Siphonostoma, Syngnathus, Doryichthys, Nci-aphis,. Protocamjms, IcMJnjocampus, Nannocampus, Urocampus, Lcpto- ichthys, Ccelonotus, Stigmatophora, Gastrotokeus, Solenognathus, Pliyllopteryx, Hippocampus. ORDER ~VI.Plectognathi. Teleosteous fishes with rough scales, or with ossifications of the- cutis in the form of scutes or spines ; skin sometimes entirely naked. Skeleton incompletely ossified, with the vertebra in small number. Gills pectinate ; a narrow gill-opening in front of the pectoral fins. Mouth narrow ; the bones of the upper jaw generally firmly united. A soft dorsal fin, belonging to the caudal portion of the vertebral column, opposite to the anal ; sometimes elements of a spinous dorsal besides. Ventral fin none, or reduced to spines. Air-bladder without pneumatic duct. Family 1. Sclcrodcrini. Snout somewhat produced ; jaws armed with distinct teeth in small number. Skin with scutes, or rough. The elements of a spinous dorsal and ventral fin generally present. Genera: Triacanthus, Baliatcs (File-Fish), Monacantlius, Anacan- thus, Ostracion (Coffer-Fish). Fossil: Acanthoderma, Acantho- plcurus, Glyptoccphalus. Family 2. Gymnodontes. Body more or less shortened. The bones of the upper and lower jaw are confluent, forming a beak with a trenchant edge, without teeth, with or without median suture. A soft dorsal, caudal, and anal are developed, approximate. No spinous dorsal. Pectoral fins ; no ventrals. Genera : Triodon, Tctrodon (Globe-Fish), Liodon (Sea-Hedge hog), Orthagoriscas (Sun-Fish) Subclass III. C yclostomata. Skeleton cartilaginous and notochordal, without ribs and without real jaws. Skull not separate from the vertebral column. No limbs. Gills in the form of fixed sacs, with out branchial arches, six or seven in number on each side. One nasal aperture only. Heart without bulbus arteriosus. Mouth anterior, surrounded by a circular or subcir- cular lip, suctorial. Alimentary canal straight, simple, without csecal appendages, pancreas, or spleen. Generative outlet peritoneal. Vertical fins rayed. The Cyclostomes are most probably a very ancient type. Unfortunately the organs of these creatures are too soft to be preserved, with the exception of the horny denticles with which the mouth of some of them is armed. Family 1. Pctromyzontidw (Lampreys). Body eel-shaped, naked. Subject to a metamorphosis ; in the perfect stage with a suctorial mouth armed with teeth, simple or multicuspid, horny, sitting on a soft papilla. Maxillary, mandibulary, lingual, and suctorial teeth may be distinguished. Eyes present (in mature animals). External nasal aperture in the middle of the upper side of the head. The nasal duct terminates without perforating the palate. Seven branchial sacs and apertures on each side behind the head ; the inner branchial ducts terminate in a separate common tube. Intes tine with a spiral valve. Eggs small. The larvce without teeth, and with a single continuous vertical fin. Genera : Pctromyzon, Mordacia, and Geotria. Family 2. Myxinidce. Body eel-shaped, naked. The single
nasal aperture is above the mouth, quite at the extremity of the
