Garcinological Fauna of India. 386 



fitigei-s : fingers slender and tapering, in the male there is an enlarged 

 tooth near the base of the dactylus. 



The legs, like the chelipeds, are rough under the lens : the edges 

 of their propodites and dactyli are finelj' plumed: none of their joints 

 are dilated : the first pair, which are slightly the longest, are about 

 If times the length of the carapace. 



In the Indian Museum are 5 specimens from the Andamans and 

 2 from the Nicobars. 



Family HYMENOSOMID^, Ortm. 



Key to the Indian Genera or Sub-genera. 



I. Front conspicuously tridentate : the external maxillipeds 

 do not quite meet across the buccal cavern and their 

 exognath is not hidden in its proximal portion : chelipeds 

 much more massive than the legs ... ... ... ... Hymenicus. 



II. Front broadly triangular, or truncated : the external 

 maxillipeds completely close the buccal cavern and their 

 exognath is completely hidden : — 



1. The interantennular septum is a prominent plate : 

 chelipeds in the male much more massive than the 



legs ... Elamexa. 



2. The interantennular septum is a mere ridge ; 

 chelipeds in both sexes slender, not stouter than 



the legs Trigonoplax. 



Elamena, Edw. 



Elamena, Milne Edwards, Hist. Nat. Crust. II. 33, and Ann. Sci. Nat,, Zool,, 

 (3) XX. 1853, p. 223 : Dana U. S. Expl. Exp. Crust, pt. I. p. 379 : A Milne Edward?, 

 Nouv. Archiv. du Mus. IX. 1873, p. 321, 



Carapace flat dorsally, thin and almost lamellar, triangular or sub- 

 circular, its edges are usually turned up to form a thin circumscribing 

 ridge and are without any teeth. Front broadly triangular, or some- 

 times truncated. There are no orbits and the eyes, though they may 

 be hidden beneath the front, are exposed and non-retractile : a small 

 post-ocular tooth may be present or not. The antenuules fold beneath 

 the front and are not visible from above when folded : the interanten- 

 nular septum is a prominent plate. Antennal peduncle slender, the 

 flagellum of no great length. 



Epistome well defined and remarkably long fore and aft. Buccal 

 cavern square ; the external maxillipeds, which completely close it, 

 have the merus about as large as the ischium, the palp articulating not 

 far from the antero-external angle of the merus, and the exognath 

 slender and concealed. 



727 



