30 



DERMATEMTD1D.E. 



lobo movable ; with four pairs of shields, of which the posterior or 

 anal are usually coalesced into a single shield ; a very small gular 

 may be present ; abdominals separated from the marginals by two 

 shields. Beak scarcely hooked ; jaws with a single sharp edge : 

 oi-bits directed upwards ; postorbital and temporal arches moderate. 

 Chin with a pair of barbels. Digits webbed. Tail short. 

 Central America. 



Fig. P. 



Skull of Staurutypus salvinii. (From Gray, P. Z. S. 1869.) 



The two species agree in the following characters : — Vertebral 

 shields not broader than long, not two thirds the width of the 

 costals ; an emarginatiou in the posterior border of each of the 

 vertebral and costal shields, corresponding to the three keels which 

 run along the carapace. Head extremely large ; a large horny 

 shield covers the upper jaw, another the mandible, and a third the 

 upper surface of the snout ; soft parts with small warts ; tympanum 

 indistinct under the thick skin. AYrist and heel with curved band- 

 like lamella3. Male with a patch of small horny, sharp-edged 

 tubercles on the lower surface of the leg and another under the 

 thigh. Tail with more or less distinct small conical tubercles, 

 forming paired longitudinal series. 



In »S^. salvinii the neural plates are seven in number, about as 

 broad as long ; the last is separated from the pygal by the seventh 

 pair of costals ; the eighth pair of costals is separated by the pygal, 

 which is either single or divided into a small anterior and a large 

 posterior plate. The hyoplastral bones have a greater share in the 

 formation of the bridge than the hypoplastrals. 



