I9I5-] 



F aima of the Chilka Lake : Crustacea Decapoda. 



217 



Unfortunately no adult males were obtained. In females and young males the 

 chelipedes are slender and, as consideration of the other characters of the species indi- 

 cate that it belongs to the sub-genus Trigonoplax rather than to Elamena, s.S., it may 

 be surmised that they are also slender in the adult male. 



In ovigerous females the chelipedes are about as long as the carapace, not stouter 

 and a great deal shorter than any of the walking legs. The carpus is about two- 

 thirds the length of the palm ; the fingers are as long as the palm and are curved 

 both horizontally and vertically; when closed, they meet only at the tips which are 

 toothed and slightly spooned. In young males the fingers appear to be a little 

 shorter than the palm. 



The first and second pairs of walking legs are about equal in length, nearly two 

 and a half times as long as the carapace, while those of the last pair are the shortest, 

 about one and a half times the length of the carapace. There are no teeth or den- 

 ticles on the upper margin of any of the segments and the dactyli, which are not 

 broader than the propodi, are set with short hairs, 

 among which, at the distal end, is a series of short 

 recurved teeth (text-fig. 5). 



The largest specimen, an ovigerous female, is 7-9 

 mm. in length. 



E. (Trigonoplax) cimex, though it agrees with E. 

 (Trigonoplax) unguiformis [ , the type and only other 

 known species of the subgenus % , in many important 

 respects, differs in several notable points, in some 

 of which it bears a significant resemblance to allied 

 genera. 



The chief points in which it agrees with typical 

 Trigonoplax are (i) the simple — not tridentate— ros- 

 trum (ii) the absence of any teeth or an upturned Propodus and dactyius of last walking leg. 

 edge on the margin of the carapace, (iii) the consider- 

 able length of the epistome, and (iv) the well-developed external maxillipedes which 

 completely close the buccal cavern. 



On the other hand the areolation of the carapace is more distinct than in the 

 other member of the sub-genus ; the carapace is proportionately much narrower ; 

 there is a distinct post-orbital tooth; the interantennular septum — represented, how- 

 ever, merely by a narrow ridge in E. (Trigonoplax) unguiformis— is wholly absent; 

 the exognath of the outer maxillipedes is not entirely hidden. 



In some at least of these characters it shows considerable resemblance to 



Fig. 5. — Elamena [Trigonoplax) 

 cimex, sp. nov. 



1 De Haan, in Siebold's Fauna Japonica, Crust., p. 75, pi. xxix, fig. 1 (1839); Alcock, Journ. 

 Asiat. Soc. Bengal, LXIX, p. 387 (1900); de Man, Trans. Linn. Soc, Zool. (2), IX, p. 396 (1907). 



a Stimpson's Trigonoplax truncata [Proc. Acad. Nat. Sei. Philadelphia, X,p. 109 (1858) and Smithson. 

 Misc. Coll., XLIX, p. 146 (i907)]'is now regarded as a member of Elamena, s.s. 



