66 Papers from the Department of Marine Biology. 
The female has the second pair of walking legs rather longer and 
much stronger than the rest. The femoral article in particular is 
strongly compressed and very broad. In fact, the lateral view of the 
female crab reminds one greatly of the burrowing Orthopteran insect 
Gryllotalpa with its stout strong first pair of legs modified for burrowing. 
Heller, in 1862, also called attention to the resemblance in general 
shape to the cylindrical wood-boring beetles. But Cryptochirus differs 
from both these cases in the fact that no active boring and burrowing is 
performed and the great development of one pair of appendages in 
both Cryptochirus and Gryllotalpa is thus due to different causes. 
Fia. 19. 
A. Cryptochirus coralliodytes in its natural position in a colony of Leptastrea roissyana. Thecrab 
e. is seen in its pit, the cup of a dead polyp, surrounded by normal polyps. It will be 
noticed that the only part of the carapace visible is the obliquely flattened anterior part; 
the chel# and the second pair of thoracic limbs fill up the space to the sides. This 
illustration does not convey quite adequately the effective way in which the pit is filled up 
by its inhabitant. 
B. C. dimorphus (after Henderson). Female and male, <8, to show the striking sexual dimorph- 
ism in this species. Compare with figures D and F of C. coralliodytes, where the male and 
female are drawn to the same scale and are more nearly the same size. 
C-F refer to C. coralliodytes. 
C. Side view of mature female, X6. The eggsin the brood pouch are indicated as seen through 
sa the transparent lateral walls of the latter. Note also the flattened anterior part of the 
a carapace, and the enlarged second pair of thoracic appendages used in movement in the pit. 
D. Ventral view of mature female, X6. Some of the developing eggs in the brood pouch are 
seen projecting from it. The immature eggs in the ovary are indicated by the dotted 
circles in the abdomen, posteriorly. 
E. Immature female, ventral view. To show narrow abdomen. 
F. Male, <6, to show size compared to mature female. The copulatory styles are represented 
by dotted lines passing beneath the abdomen, emerging at its anterior end. 
x 
