Fishes . The numerous genera of this order arereferred to three famihes, the Palcconiscidw, Platysomida:, andDiciyopygidic; a fourth family, Dorypteridcc, of uncertain re-lations, being also tentatively recognized. The family ofPaUroniscidce is the most primitive, ranging from the Devonianto the Lias, and some of them seem to have entered freshwaters in the time of the coal-measures. These fishes havethe body elongate and provided with one short dorsal fin. Thetail is heterocercal and the body covered with rhombic or rudimentary spine-like scales are developed on theupper edge of
Fishes . The numerous genera of this order arereferred to three famihes, the Palcconiscidw, Platysomida:, andDiciyopygidic; a fourth family, Dorypteridcc, of uncertain re-lations, being also tentatively recognized. The family ofPaUroniscidce is the most primitive, ranging from the Devonianto the Lias, and some of them seem to have entered freshwaters in the time of the coal-measures. These fishes havethe body elongate and provided with one short dorsal fin. Thetail is heterocercal and the body covered with rhombic or rudimentary spine-like scales are developed on theupper edge of the caudal fin in most recent Ganoids, and oftenthe back has a median row of undeveloped scales. A multi-tude of species and genera are recorded A typical form isthe genus Palcconisciiin* with many species represented in therocks of various parts of the world. The longest known speciesis PalcEonisciim jrieslebenense from the Permian of Germanyand England. Palcconiscnm magnum, sixteen inches long, occurs. Fig. 185.âPalaoniscum frieslebenenxc Ulaiiiville. Family Pataoniscida. (After Zittel.) in the Permian of Germany. From Canohius, the most primi-tive genus, to Coccolepis, the most modem, is a continuous series,the .suspensorium of the lower jaw becoming more oblique,the basal bones of the dorsal fewer, the dorsal extending fartherforward, and the scales more completely imbricate. Otherprominent genera are Amhlypteriis, Eurylepis, Cheirolepis,Rhadinichthys, Pygoptcriis, Elonichthys, JErolepis, Gyrolepis,Myriolepis, Oxygnathits, Centrolepis, and Holnrus. The Platysomidae. â The Platysomida; are different in fnnn,the body being deep and compressed, often diamond-shaped, ⦠This word is usually written Palceoniscus, but Blainville, its author (1818),chose the neuter form. The Ganoids 251 with very long dorsal and anal fins. In other respects they arevery similar to the Palceoniscidcc, the osteology being the Palcconiscida: were rapacious fishes with sharp teeth, thePl
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