CATALOGUE 



OF 



FOSSIL REPTILIA 



AND 



AMPHIBIA. 



Class REPTILIA. 



SYNAPTOSAUEIAN BRANCH' (continued). 



Order CHELONIA. 



Body short and wide, and usually encased in a more or less complete 

 bony shell, of which the ventral portion, or plastron, consists of a 

 few elements of dermal origin ; while the carapace may be in great 

 part of endoskeletal derivation. Frequently a horny epidermal 

 exoskeleton. Neck usually short, and if comparatively long with 

 but few vertebrae ; tail short or of moderate length. Inferior 

 temporal arcade usually present, and in some instances also a 

 superior arcade ; narial aperture single and terminal ; premaxilla 

 very small ; no parietal foramen in the adult ; no transverse bone ; 

 a large opisthotic ; post orbital welded with postfrontal, and usually 

 the nasal with the prefrontal; mandibular symphysis generally 

 anchylosed. Palate completely closed by junction of the pterygoids 

 with the basisphenoid, and frequently also with one another. 



1 See Part II. p. 118. 

 PART III. B 



