166 



NATURAL HISTORY OF OUR SHORES 



A little group of crabs that live on open shores 

 and bury in the sand for protection is named the 

 Corystidce. 



Its representative is Corystes cassivelaunus, sometimes 

 called the " Masked Crab " (Fig. 71). 



This species has an oval body, about an inch broad, and 

 about the same in thickness, and about one and a half inches 

 long an unusual proportion in the short-tailed crabs. 

 It has long ^straight, Jeathery antennae. In the male the 



claws are long and straight, 

 in the female shorter and 

 incurved. Its colour is 

 greyish white. It may often 

 be found buried in the 

 sand, with just its antennae 

 and claw tips projecting. 



Atelicydus heterodon is a 

 species with a circular shell, 

 about an inch and a half 

 in diameter. The edges of 

 the carapace are strongly 

 toothed, and this part, as 

 well as the limbs, is fur- 

 nished with hairs. The colour is pink. It is less common 

 than the preceding. 



The most curious and beautiful of these sand crabs is 

 Thia polita (Fig. 72). This crab, which is only an inch 

 across the carapace, is ivory-white, delicately spotted with 

 pink. The shell is highly polished. Its shape is peculiar : 

 the shell of the carapace being rounded in one direction 

 only, from side to side. 



It has, I believe, no popular name, beyond the precincts 

 of this household, where the junior members have 

 termed it the " Thumb-nail Crab," a name which well 

 describes its form. 



Fig. 72 

 Thia polita. f Natural size 



