PLATYSTEENUM. 



Carapace much depressed, oval, with a feeble median keel poste- 

 riorly ; anterior border broadly emarginate. Nuchal shield very 

 small, broader than long ; vertebrals broader than long, as broad 

 as the costals or a little narrower, much broader in the young, 

 in which the posterior border of the carapace is distinctly serrated. 



V 



Fig. 13. Skull of Platysternum megaccphal; 



Front lobe of plastron squarish, posterior angularly emarginate ; 

 the width of the bridge contained four or five times in the length 

 of the plastron ; the longest plastral shields are the anals, femorals, 

 and humerals ; the shortest the gulars, which occupy, however, 

 the whole width of the front border of the plastron ; frequently a 

 small intergular shield between the gulars and the humerals. 

 Upper surface of head and temple with an undivided horny scute. 



