346 



ZOOLOGY 



the row of neural plates. The neural plates are absent in some 

 cases (Chdodina). 



Po 



FIG. 985. Anterior vertebrae of young Crocodile. A. atlas; Ep. axis; IS. intervertebral 

 discs; 0. pro-atlas; Ob. neural arches-; Po. odontoid bone; Ps. spinous processes ; Pt. 

 transverse processes ; R. R.^ R.'* ribs ; s. arch of--atlas ; v.. median piece of atlas ; WK. centra. 

 (From Wicdersheim's Comparative Anatomy.) 



Fio. 986. Cistudo lutaria. Skeleton seen from below ; the plastron has been removed and 

 is represented on one side. C. costal plate ; Co. coracoid ; e. entoplastron (episUrnum); 

 Ep. epiplastron (clavicle?); F. fibula; Fe. femur; H. humerus ; Hup. hyoplastron ; Itpp; 

 hypoplastrou ; Jl. ilium ; Js. ischium ; M. marginal plates ; Ku. nuchal plate ; PI. pubis ; 

 Pro. procoracoid or process of scapula ; Py. pygal plates ; R. radius ; Sc. scapula ; T. tibia ; 

 U. ulna ; Xp. xiphiplastron. (From Zittel.) 



The bony elements of the plastron of the Chelonia are an 

 anterior and median plate, or entoplastron, and four pairs of plates 



