1KB 



Comparative Morphology of Chordates 



vb I 



Fig. 377. Parietal eye of the legless lizard. Angais fragilis. (cl) Connective- 

 tissue cells around nerve; (gc) ganglion-cells; (I) lens; (n) nerve-fibers; (pn) parietal 

 nerve; (pc) pigment-cells; (r) retinal cells; (vb) vitreous body. (After Nowikoff. 

 Courtesy, Kingsley: "Comparative Anatomy of Vertebrates," Philadelphia, The 

 Blakiston Company.) 



Fig. 378. Chirotes, an almost legless lizard. (Courtesy, Brehm: "Tierleben," Leipzig, 

 Bibliographisches Institut.) 



elastic ligament. No sternum. .Movable eyelids, tympanic cavity 

 and membrane are lacking. Parietal organ not eyelike. No urinary 

 bladder. Many snakes are viviparous. 



In snakes, as in lizards, the movable quadrate increases the 

 extent to which the mouth may be opened, but in snakes the potential 

 "gape" is further greatly increased by the elastic connections of the 

 several bones of the upper jaw and of the two rami of the lower jaw 



