STERNOTHERTJS SINUATUS. 



intergular plate five-sided ; brachial plates rhomboidal ; pectoral plates 

 at their commissure with each other narrow, the posterior edges straight, the 

 anterior oblique, owing to which circumstance the outer sides are much wider 

 than the inner ; anal plates triangular. Head broad and depressed ; nose 

 short and rounded ; the fronto-nasal plates forming a portion of the hinder 

 edges of the orbits ; the frontal plate very large and inclined to six-sided ; the 

 parietal plates oblong, and broadest in front ; the post-orbital plate small and 

 oval. The apex of upper mandible emarginate with an obtuse tooth-like process 

 on each side of the emargination ; the tip of the lower mandible produced and 

 directed upwards ; under the chin two minute barbels. Neck and legs 

 sparingly covered by small scales ; the hinder edge of each fore leg towards the 

 toes with a broad fringe of thin delicate plates ; the toes short and armed with 

 strong claws nearly straight and slightly concave below. The posterior edges 

 of the hinder feet also with a continuous fringe of thin scales, the outermost 

 toe rudimentary, the second and innermost nearly of equal length, and shorter 

 than the third and fourth. Tail rather long, pointed and somewhat cylindrical. 



DIMENSIONS. 



Inches. Lines. 

 Breadth of shell across femoral plates. . . 9 3 



Lengthoftail 2 5 



of sternum from anterior to 



hinder edge 13 3 



Inches. Lines. 

 Length from nose to hinder margin of 



shell 19 



of head and neck 5 6 



of shell 14 5 



Height of shell 5 3 



The colours in the female are nearly similar to those of the male. In both 

 sexes the head, neck, and anterior extremities, when retracted, are completely 

 protected by the anterior portion of the sternum, which by means of the joint 

 in front of the abdominal plates is closely applied to the anterior margin of the 

 upper shell. The principal differences between this species and Stemotherus 

 ater and S. castaneus will be found in the general form of the shell, the shape 

 of the plates, and the structure of the tip of the upper mandible. 



The first specimens of this tortoise were discovered in rivers to the north of 25° south lati- 

 tude, and in situations only where the water was very deep. They were usually observed dur- 

 ing the heat of the day lying upon rocks which projected above the surface of the water, and 

 were so vigilant that it was almost impossible to approach them within a moderate distance, 

 before they vanished. Many of them were struck by musket balls, yet no wounds which were 

 thus inflicted ever appeared to impede their movements. At last, by means of hooks baited 

 with flesh we succeeded in obtaining a few specimens, though against such means they were 

 also guarded ; for even where individuals existed in abundance, perhaps not one could be se- 

 cured by four or five fishermen, after spending many hours in the pursuit. Between 24° and 

 25° they occurred in greatest abundance, probably from the circumstance that between those 

 parallels the pools were deepest ; to the north of the former parallel they appeared to be scarce, 

 owing no doubt to the channels of the streams being there loaded with gravel and sand. 



