. The chordates. Chordata. 432 Comparative Morphology of Chordates Of living fishes, the only members of Holostei are the gar pike (Lepidosteus) and the "mudfish" or "bow-fin" (Amia). Both arc North American fresh-water fishes (Fig. 333C, D). The vertebrae of Lepidosteus are exceptional for fishes in being convex in front and con- cave behind (opisthocoelous). The "alligator gar" may attain a length of 10 feet. Amia is a comparatively small fish. Order Teleostei "Bony ; Ossification of skeleton at the maximum for fishes (Figs. 334, 335). (The name
. The chordates. Chordata. 432 Comparative Morphology of Chordates Of living fishes, the only members of Holostei are the gar pike (Lepidosteus) and the "mudfish" or "bow-fin" (Amia). Both arc North American fresh-water fishes (Fig. 333C, D). The vertebrae of Lepidosteus are exceptional for fishes in being convex in front and con- cave behind (opisthocoelous). The "alligator gar" may attain a length of 10 feet. Amia is a comparatively small fish. Order Teleostei "Bony ; Ossification of skeleton at the maximum for fishes (Figs. 334, 335). (The name "Teleostei," meaning "completely bony," is not to be confused with "Teleostomi," referring to the terminal mouth.) Tail-fin homocercal or diphycercal (Figs. 327, 334). Pelvic fins more or less reduced or sometimes lacking, and com- monly placed more or less in front of their typical position at the rear end of the trunk, in extreme cases (, the cod and its allies, Gadidae) lying actually anterior to the pectoral fins (Fig. 299). In some eels, both pairs of fins absent. Scales usually simple, thin, overlapping plates of bone developed in lower layer (dermis) of skin (Fig. 328); sometimes elaborated into projecting spines (porcupine fishes) or other specialized forms; sometimes lacking (eels, swordfish, many catfishes). Spiracles always closed; five pairs of gill-clefts or in some cases fewer. Intestine has no spiral valve other than possible vestiges of it in a few cases. SUPRAOCCIPITALl BASIOCCIPiTAl: HYOMANDIBULAR> SQUAMOSALS ST VERTEBRA NEURAL SPINE PAR I ETAL- PARASPHENOID' PTERYGOIDS>^<^ FRONTAL"^<Wn§ ECTETHMO ID-y25d£2^^^ MESETHMOID NASAL— ,„ W///m. MAX ILLA PREMAXILLA ARTICULAR DENTARY- \!SRANCHIOSTEGAL ^fe^i*1- KAY1> ARCHES ( Fig. 335. Skull of hake in left lateral aspect. Membrane bones are cross- hatched, cartilage bones stippled. Compared with the skulls of other fishes, that of teleosts shows an increased d
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