40 
THE EACES OF ALDABEA. 
Nothing is known of the history of the half^grown male, beyond that it was a dona- 
tion from Sir Joseph Banks in 1810. 
The cara])ace (Plate VII.) is very regularly shaped, scarcely wider behind than in 
front, with the anterior and posterior margins slightly reverted, and with very shallow 
notches between the marginal plates. It is rather high, with the sides nearly perpen- 
dicular, and with the centre of each of the vertebral plates slightly raised. Nuchal 
excision very shallow. Fore part of the shell declivous from the centre of the second 
dorsal plate. Caudal scute not reverted, but rather convex. The plates of the back, 
as well as the sternum, are perfectly smooth, without a trace of concentric strise. 
Nuchal plate narrow in its upper, and much dilated in its lower portion. 
The sternum has no excision, either in front or behind. The lateral edges of its 
front lobe are somewhat emarginate, not convex. As in all adult males, the sternum 
is deeply hollowed out and provided with thick callosities on the sides and behind. 
This is already conspicuous in the young male. 
Both carapaces are entirely of a uniform deep black colour. 
The bony substance of the shell is not particularly thick. 
I subjoin the measurements of these three specimens : — 
Length of carapace. Width of carapace. Depth of Sternum. Caudal plate. 
In str. line. Over curve. In str. line. Over curve, carapace. Length. Width. Length. Width. 
Spec. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
in. 
Ad. c?(1021). 
36 
47i 
22 
48 
16 
251 
21 
3 
9 
H.-gr. d (1020). 
23 
281 
14 
28 
11 
17 
13 
H 
Ad. $ (living) . 
32 
391 
31 
421 
161 
25 
201 
31 
7 
