. The chordates. Chordata. 486 Comparative Morphology of Chordates. Fig. 375. {Left and Center) Skull of a lizard (Gerrhontus imbricatus). (After Siebenrock.) (Right) Skull of snake, Tropidonotus. (After Parker.) (av) articular; (bo) basioccipital; (bs) basisphenoid; (d) dentale; (eo) exoccipital; (epo) epiotic; (/) frontal; (j) jugal; (mi) maxilla; (n) nasal; (oo) opistbotic; (p) parietal; (pf) postfrontal; (pi) palatine; (pm, pmx) premaxilla; (prf) prefrontal; (pro) prootic; (pt) pterygoid; (a) quadrate; (qj) quadratojugal; (sa) supra-angular; (sbo) subocular; (so) supraoccipital; (spt) supr
. The chordates. Chordata. 486 Comparative Morphology of Chordates. Fig. 375. {Left and Center) Skull of a lizard (Gerrhontus imbricatus). (After Siebenrock.) (Right) Skull of snake, Tropidonotus. (After Parker.) (av) articular; (bo) basioccipital; (bs) basisphenoid; (d) dentale; (eo) exoccipital; (epo) epiotic; (/) frontal; (j) jugal; (mi) maxilla; (n) nasal; (oo) opistbotic; (p) parietal; (pf) postfrontal; (pi) palatine; (pm, pmx) premaxilla; (prf) prefrontal; (pro) prootic; (pt) pterygoid; (a) quadrate; (qj) quadratojugal; (sa) supra-angular; (sbo) subocular; (so) supraoccipital; (spt) supratemporal; (sq) squamosal; (tr) transversum; (v) vomer. (Courtesy, Kingsley: "Comparative Anatomy of Vertebrates," Phila- delphia, The Blakiston Company.) tympanic auditory apparatus and the parietal eye (Fig. 377) usually well developed. Urinary bladder present in most groups. Some lizards are viviparous. Some lizards are exceptional in that, in varying degree, the body is elongated and the legs are reduced (Fig. 378)—a condition culmi- nating in the "legless lizards," Amphisbaenia. These burrowing animals appear snakelike, having no external legs, although vestiges of girdles may persist. The sternum is reduced or absent. The tympanic structures of the ear are less well developed than in typical lizards. The urinary bladder is lacking, as in snakes. Order Serpentes (Ophidia) Snakes (Fig. 379). Body much elongated and cylindric. No legs, although occasional vestiges of the pelvic (but never the pectoral) girdle occur and in pythons there are vestiges of hindlegs appearing externally as a pair of clawlike projections (Fig. 380). Bones of upper jaw (maxillary, palatine, pterygoid) movably joined by elastic ligaments. Bight and left halves (rami) of lower jaw joined in front by. 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
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