298 Memoirs of the Indian Museum. [Voi,. V, 



the genus. The third pair, which is the longest, reaches beyond the apex of the 

 antennal scale by the length of the dactylus ; the fifth reach almost to the end of the 

 second segment of the antennular peduncle. In the third pair the carpus is a little 

 longer than the propodus, nearly one and a half times the length of the ischium, and 

 about three quarters as long as the merus. The latter segment is eight times as long 

 as broad. The dactylus is slender, slightly curved, and terminates in a very fine 

 claw which is nearly as long as the segment proper. The propodus is about 17 times 

 the entire length of the dactylus. 



In the fifth peraeopods there is a series of setae, not found on the two preceding 

 pairs of limbs, at the distal end of the propodus on its inferior surface. The carpus 

 is one-fifth shorter than the propodus, the latter segment being about equal in length 

 with the merus. The merus is eight times as long as wide and about twice the length 

 of the ischium; the dactylus has the same proportion to the propodus as in the third 

 leg (text-fig. 32/). 



The branchial formula is apparently the same as in other species of the genus ; 

 epipods fC en crochet " (epipod a of Coutière's terminology) are present on the first 

 three peraeopods. 1 



The abdominal pleura are rounded, except for that of the fifth somite, which is 

 acutely pointed behind, and for the posterior angle of the sixth, which is also acute 

 and articulated as in other species of Athanas. 



The appendix masculina is well developed in all the males and is about the same 

 length as the appendix interna. 



The telson (text-fig. 32g) is as long as the uropods. It is a little less than four 

 times as long as the breadth between the posterior angles and bears two pairs of 

 dorso-lateral spinules. The margin between the two pairs of postero-lateral spinules 

 is gently rounded and fringed with long setae, each seta being markedly swollen at 

 the base. The inner of the two pairs of spinules is more than twice as long as the 

 outer, both extending beyond the apex of the median portion. The outer uropod 

 (text-fig. 32A) bears a fringe of setae on the under side, running parallel with, and 

 close to, the external margin ; it is a little more than twice as long as broad. 



A large male is only about 15 mm. in total length; the ovigerous females do 

 not exceed 13 mm. 



Athanas polymorphus is evidently closely allied to Ortmann's A. dimorphus 2 and 

 would find a place next that species in the admirable key which de Man has provided 

 (loc. cit., p. 289, footnote). Both sexes of the Chilka Lake species are readily distin- 

 guished from A . dimorphus by the presence of a spine near the antero-lateral angle of 

 the carapace, while males may be separated at a glance by the spines on the inferior 

 edge of the merus in the enlarged first leg. From all other species in the same sec- 

 tion of the genus it is distinguished by the great length of the carpus in the first legs 

 of the female. 



1 See Coutièie, Ann. Sei. nat., Zool. (8), IX, pp. 276, 277 (1899). 



% Ortmann, in Semon's Zool. Forschungsreis, in Australien, etc., V, p. 12, pi. I, fig. 1 (1894). 



