116 A. Alcock — Neiv and Rare Species of Crustacea. [No. 2, 



pair : they terminate in a very perfect chela of comparatively large 

 size, with the dactylus anterior (or dorsal). The fourth pair reach 

 just beyond the far end of the merus of the third pair : they end in 

 a very much smaller and less perfect chela, with the dactylus posterior 

 (or ventral). 



The abdomen is a perfectly soft membranous bag, of which the 

 segmentation is quite recognizably, but far from conspicuously, defined. 

 In the male it is symmetrical, though the minute or rudimentary 

 appendages, that are present on one side (right or left) of the 3rd 4th 

 and 5th segments, are represented on the other side only by small tufts 

 of small bristles. In the female its symmetry is lost by the presence, 

 on one side or other, of a large membranous leaf -like lobe that forms 

 a capacious cup-like brood-pouch. 



The first two pairs of abdominal appendages of the male end in 

 convoluted plates, the second pair working in the grooves formed by 

 the first pair. 



The telson is quite symmetrical, and lies in the middle line, tucked 

 up against the ventral surface of the abdomen. On either side of it 

 are the quite symmetrical swimmerets of the sixth pair : the basipodite 

 of these has a spine at its posterior angle : both the exopodite and 

 endopodite are narrow slender and falciform, with the anterior edge 

 serrated and the tip spiniform : the exopodite is many times larger 

 than the endopodite. 



The animal does not inhabit a shell, but is protected by the 

 soft fleshy coenosarc of a colony of Actiniarian polyps. This forms a 

 sort of sheet or blanket, one end of which is tucked round the telson 

 of the crab and is firmly held by the hook-like swimmerets of the 6th 

 abdominal somite and by the folded-in telson, while the corners of the 

 other end are firmly grasped by the chelse of the penultimate thoracic 

 appendages in such a way that the sheet can be drawn right over the 

 back of the crab as far as the eyes. 



The colour of the crab is red : the coenosarc of the polyp-colony 

 is bluish, the polyps themselves are dark purple. 



A large male, lying in the natural position with the telson bent 

 under, measures, from the tip of the rostrum, 63 millim. ; and the 

 chelipeds of the same individual, measured along their convex curve, 

 are 68 millim. in length. 



An egg-laden female measured in the same way, is 37 millim. long 

 and has chelipeds 35 millim. long. 



205 specimens, representing both sexes in all stages, were dredged 

 by the Investigator off Cape Comorin, in 102 fathoms. 



I have much pleasure in dedicating this species to Captain A. R. S. 



