[Vol. V, 1921.] Fauna of the Chilka Lake : Amphipoda. 551 



loped in the more immature forms. Figure ioô represents the upper antenna of a 

 male whose first gnathopod is shown in fig. io<s, a male which I consider to be not 

 quite fully mature ; in older males the characters of the antennae are still more 

 pronounced. 



The mouth parts have already been described and figured by Stebbing and do 

 not call for detailed description. The outer lobes of the lower lip (fig. lod) bear on 

 their strongly convex margin a number of fine setules, one of which is much stouter 

 than the rest and is divided distally, giving an appearance as if several of the setae 

 had fused at the base. 



The gnathopoda of the male of this form have been described by Coutière and 

 Stebbing and are shown in figs. 100, /, g. 



The gnathopods of the female are shown in figs. 10h and k, corresponding very 

 closely with the description and figures given by Stebbing. The first gnathopod is 

 of the same general structure as the second but considerably stouter ; the carpus is 

 wide with its posterior margin strongly convex and setose; the propod widens 

 distally, the palm being somewhat oblique and the finger is elongated and strongly 

 curved towards the apex, its inner margin being serrate. 



The peraeopoda do not require detailed description. The posterior pairs, especi- 

 ally the fifth, become greatly elongated in fully adult specimens, especially in the 

 males. 



The uropoda (fig. 10/) are closely similar to those of A or a except that the third 

 one has only one branch. This branch is about twice as long as the peduncle and 

 does not extend beyond the end of the second uropod. 



The telson is broadened above and on each side ends in a sharp curved tooth 

 with one or two slender setules. It closely resembles that of Aora typica. 



Besides the form described above there appears to be another form of the male 

 with differently shaped first gnathopods. As already stated, in immature males of 

 the first form there is often found a small tooth on the posterior margin of the carpus 

 as shown in fig. 100. In the usual form of male this tooth is not further developed, 

 but the carpus becomes massive and more elongated and the finger thickened as shown 

 in the figure given by Coutière. In other forms, however, the tooth becomes much 

 more elongated and prominent and the postero-distal angle of the carpus develops 

 into a long pointed tooth, the base of which occupies nearly the whole of the palm ; 

 at the same time the antero-basal corner of the carpus becomes produced backwards 

 into a well marked rounded lobe, overlapped on the outer side by a wide flange deve- 

 loped on the basis. These points are shown in fig. iow, which is a fairly young 

 male of this second form. It will be seen that there is scarcely any palm on the 

 carpus, that the propod is somewhat narrowed at the base, widening afterwards and 

 that it bears on its posterior margin a stout triangular tooth about one-third of its 

 length from the apex. The finger is long, not greatly thickened, ending acutely and 

 overlapping the tooth on the posterior margin of the carpus. The subsequent deve- 

 lopment of this appendage can be seen by comparing figures ion and 0, with fig. 

 10m. Fig. 10» shows the limb folded up, when it is difficult to distinguish the 



