28 



DERMATEMTDID.^. 



Carapace much depressed ; marginal shields, one azygos nuchal 

 and 12 pairs. Plastron large, extensively united to the cara- 

 pace by suture, with short axillary and inguinal buttresses, the 

 former just reaching the first costal plate, the latter terminating on 

 the eightli marginal. 8ix pairs of plastral shields, the anterior 

 (gular) usually fused ; a series of inframarginals separates the mar- 

 ginal from the plastral shields. Skull with a bony temporal arch ; 



Shell of Dermatemys mawii *. 



alveolar surfaces verj' broad, of upper jaw with a strong denticulated 

 median ridge and a short perpendicular one in front ; lower jaw 

 with two cutting-edges on each side, which are connected anteriorly 

 by a short perpendicular ridge ; edge of jaws toothed. Digits very 

 broadly webbed. Tail very short. 

 Central America. 



1. Dermatemys mawii. 



Dermatemvs mawii, Gray, Proc. Zool. Soc. l5<47, and Cat. Sh. liept. i. 

 p. 49, pi. xxi. (1855) ; Ccqye, Proc. Ac. PJiilad. 1SG8, p. 120 ; P. de 



* In this and in the following figures tho crosses on the earapaoe indicate 

 the position of tlie extremity of the axilhiry and inguinal peduncles of the 

 plastron, which nnchylose with the lower surface of the carapace. 



