. The chordates. Chordata. lchthyopsida 427. Ji y X Fig. 330. (Top) Rhinobatus lentiginosus (Garman): in form of body, inter- mediate between an ordinary sbark and the very broad thin skate. (Bottom) Raja erinacea (Mitchill). (Courtesy, Jordan and Evermann: "Fishes of North and Middle America," Washington, The Smithsonian Institution.) connection with the pharynx. This air-bladder may serve as an acces- sory respiratory organ (when open into the pharynx) or it may have a hydrostatic function, making possible the adjustment of the specific gravity of the fish to that of the water by c
. The chordates. Chordata. lchthyopsida 427. Ji y X Fig. 330. (Top) Rhinobatus lentiginosus (Garman): in form of body, inter- mediate between an ordinary sbark and the very broad thin skate. (Bottom) Raja erinacea (Mitchill). (Courtesy, Jordan and Evermann: "Fishes of North and Middle America," Washington, The Smithsonian Institution.) connection with the pharynx. This air-bladder may serve as an acces- sory respiratory organ (when open into the pharynx) or it may have a hydrostatic function, making possible the adjustment of the specific gravity of the fish to that of the water by changes in the volume of gas within the air-bladder. In some fishes the organ probably serves both functions. The gas within the closed air-bladder is mainly oxygen de- rived by diffusion from blood contained in vessels in the wall of the organ. The volume of gas in the bladder may, on occasion, be reduced by absorption into the blood. The following subdivisions of Actinopterygii are generally recog- nized. Order Chondrostei Notochord fully persistent; vertebrae represented only by carti- laginous or partly bony arches—no centra. Skull largely Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : Blakiston
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