86 THE RACES OF THE GALAPAGOS. 
features of this species, of which the white colouring of the jaws and upper part of the 
head and of some of the nails is not the least singular ; it is, perhaps, an instance of 
commencing albinism. The circumstance that no young individuals or females were 
found must be accounted for by the greater difficulty of discovering small individuals, 
as well as by the well-known fact that the females are much less active, and more dis- 
inclined to leave their hiding-places, than the males. 
The anterior portion of the carapace (Plates XL. & XLI.) is narrow, compressed, and 
deep; the posterior more depressed and dilated. The upper profile is almost straight, 
and ascending forwards almost from the areolar centre of the last scute, the highest 
point of the shell being quite in front, so that the anterior aperture assumes the shape 
of a triangle pointed at the apex. The fore part of the shell is strongly compressed, 
concave on each side, with the anterior margin strongly reverted, having the appearance 
of a " Spanish saddle " in a still more marked degree than in T. epMpinum. Pos- 
teriorly the carapace is dilated, with rounded posterior margin, with a rather steep 
decline over the caudal plate, which is bent inwards, but more gently declivous on the 
sides, the marginal plates above the hind legs being strongly bulged outwards, and the 
posterior marginals being slightly reverted. The anterior margins of the shell are 
irregularly scalloped and more or less broken, as it is this part of the shell chiefly with 
which the males butt each other in their combats. The posterior margin of the cara- 
pace shows scarcely any indentation. The plates are without any trace of striation ; but 
the whole surface of the shell is deeply and irregularly pitted. 
The sternum is deeply concave, truncated in front and behind, with the front lobe 
rather contracted. 
The jaws, some of the nails, and portions of the sternum are of a yellowish white 
colour. The tail is not very long, and without terminal claw. 
Length of carapace. Width of carapace. Depth of Sternum. Postgular plates. 
In str. lino. Over curve. In str. line. Over curve. carapace. Length. Width. Length. Width, 
in. in. in. in. in. in. in. in. in. 
38 40i 22^ 38 19^ 26 21^ 7 12 
Shdl (Plate XLV. figs. D-F). — The three skulls of this Tortoise are perfectly iden- 
tical, showing more especially the same singular formation of the palate. The palate is 
narrow and very concave, bordered by the expanded pterygoid-edges, which rapidly 
converge behind. In a skull 4f inches long the foramina palatina are 23 millims. distant 
from each other, and the posterior roots of the pterygoid-edges 16 millims. The dis- 
tance of a foramen palatinum from the anterior extremity of the vomer is 32 millims. 
The inner margin of the pterygoid-edge is continued backwards as a sharp ridge over 
the base of the skull. The impression in front of the occipital condyle is deep. 
Parietal crest almost in a line with the upper surface of the skull, and long. Articular 
surface of the mandible much dilated. 
