28 DERMATEMYDID&®. 
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 eighth marginal. Six 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 ; 
Fig. 8. 
Shell of Dermatemys mawii *. 
alveolar surfaces very 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. 
Dermatemys mawii, Gray, Proc. Zool, Soc, 1847, and Cat. Sh, Rept. i. 
p- 49, pl. xxi. (1855); Cope, Proc. Ac. Philad. 1868, p. 120; LP. de 
* In this and in the following figures the crosses on the carapace indicate 
the position of the extremity of the axillary and inguinal peduncles of the 
plastron, which anchylose with the lower surface of the carapace. 
