STERNOTHERUS 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 pioduced 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. 
Length from nose to hinder margin of 
shell 19 0 
of head and neck 5 6 
of shell 14 5 
Height of shell . v . 5 3 
The colours in th e 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 anterioi margin of the 
upper shell. The principal differences between this species and Sternotherus 
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 dui- 
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 ioo s aitecl 
with flesh we succeeded in obtaining a few specimens, though against such means they viere 
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, 
Qw ing no doubt to the channels of the streams being there loaded with gravel and sand. 
iuuucs. JuiJJica. 
Breadth of shell across femoral plates ... 9 
Length of tail 2 
of sternum from anterior to 
hinder edge 13 
