344* A. Alcock — Garcinological Fauna of India. [No. 3, 



Orbits very capacious, occupying the whole face of the carapace 

 between the front and the antero-lateral angles on either side, usually 

 not very deep : their floor is divided into two fossa?, one for the bnsal 

 portions of the eyestalk, the other for the eye. The basal joint of the 

 eyestalk is visible throughout: the eye chiefly occupies the ventral 

 surface of the eyestalk, and is often, but not always, tipped by a horn 

 or style formed by a prolongation of the latter. 



The basal antennular joint is visible, but the rudimentary antennu- 

 lar flagellum is quite hidden beneath the front. The antennae, which 

 lie in the orbital hiatus, are, though properly formed in all their parts, 

 little more than rudiments. 



The epistome, though short, is quite distinct, and is sculptured. 

 The buccal cavern (in its widest part) is as broad as long, but dimi- 

 nishes in size a little, anteriorly : it is completely closed by the external 

 maxillipeds, which are somewhat narrow and elongate and end in a 

 coarse flagellum that articulates with the antero-external angle of the 

 merus. 



Chelipeds shorter than the legs and, in both sexes, remarkably 

 unequal, the larger one being much more massive than the legs. The 

 palm is short and high — especially in the larger cheliped — and is 

 almost always compressed — especially so in the smaller cheliped : the 

 fingers are stout, usually compressed, and strongly toothed. In most 

 cases there is, on the inner surface of the larger palm, near the fingers, 

 a stridulating organ, which can be scraped against the inner surface of 

 the ischium. 



Legs stout, the fourth pair much shorter and somewhat less 

 massive than the first three pair, which are of about equal length : 

 between the basal joints of the 2nd and 3rd pair is an orifice, thickly 

 protected by hairs, leading towards the branchial cavity. The branchial 

 cavity is very capacious, and its lining membrane is thick spongy and 

 vascular. 



The abdomen of the male is narrow : in both sexes it consists of 

 seven separate segments. 



Distribution : Tropical and subtropical coasts, from the American 

 Atlantic, through the Mediterranean and Red Seas, to the American 

 Pacific. 



The Ocypodes live together in large companies, and most of them are in the 

 habit of digging long and tortuous burrows in the moist sand near high-water mark, 

 into which they retire with great rapidity when alarmed. Asa rule they do not 

 go far from their burrows, but if they do happen to wander and are cut off, they run 

 to sea with marvellous speed. Though the burrows can be but temporary struc- 

 tures, each individual crab, in all the species that I have observed, keeps rigidly to 

 its own. The efficacy of the stridulating-organ as a musical instrument is beyond 



