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 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.
Length from nose to hinder margin of
shell...................................... 19 0
of head and neck ..................... 5 6
of shell...................................... 14 5
Height of shell .............. 5 3
Inches. Lines.
Breadth of shell across femoral plates. 9 3
Length of tail__~ ................................. 2 5
of sternum from anterior to ’
hinder edge ......................... 13 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 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 latitude,
and in situations only where the water was very deep. They were usually observed during
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 secured
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.