290 Dr. J. E. Gray on Chelonians. 



front and concave over the hinder cross suture ; some spe- 

 cimens of Sternotlicerus have a rather concave sternum ; and 

 some Hydromedusce have a deep narrow concavity in the 

 middle of the hinder part of the sternum ; but we have no 

 proof of these being characters of the males. 



Testudo tahidata. 



There is a considerable difference in the shields of the head. 

 Some have a pair of large plates before the large frontal ; 

 this pair varies in size. It is divided by a straight linear 

 suture and is sometimes large ; but in one specimen (e) it is 

 moderate and hexagonal, with a plate in the middle before it ; 

 in another (a) there is a single central plate over the nostrils, 

 and a large suborbital plate on each side of it; and in a third (/) 

 tliere are two central nasal hexagonal plates, one behind the 

 other, and a large plate on each side of the suture between 

 them. In general the frontal plate is large and entire, but 

 in some specimens it is divided in half. 



Peltastes geometricus. 



Four of the larger specimens in the British Museum have a 

 large, very convex, and much inflexed caudal plate, and are 

 perhaps males, as the three larger ones have the centre of the 

 sternum more or less concave : the smaller one has this part 

 flat ; and the caudal plate is convex, but not to the extent of the 

 larger ones. Three of the small specimens indicate a more 

 or less inclination to become convex ; while five, of about the 

 same size, have this plate quite flat, with a more or less reflexed 

 lower edge. 



Peltastes tentorius. 



One specimen, received from Mr. R. Brown, has the caudal 

 plate very convex and inflexed — most probably a male. In all 

 the other seven specimens in the Museum the caudal plate is 

 flatter and spread out. 



Peltastes stellatus. 



The anal notch angular, broad apparently in both sexes. 

 Hinder part of thighs with a large group of conical acute scales. 



The males have a sternum slightly concave the whole length 

 of the central line. Caudal plate very broad, convex, with a 

 strongly inflexed lower edge. 



The females have a flat sternum and only slightly convex 

 caudal plates, the lower edge of which is not inflexed. 



Peltastes platynotus. 

 The two specimens in the Museum have quite flat sternums, 



