150 Memoirs of the Indian Museum. [Vol. V, 



and Potamomysis assimilis) are very abundant in all parts of the lake, the main area 

 as well as the outer channel ; while one {Gastrosaccus muticus) has been found less com 

 monly in the outer channel and adjacent parts of the main area. The fifth species 

 (Indomysis annandalei) is at present known only from the neighbourhood of Bombay 

 The following key will serve for the identification of the known species of Indian 

 brackish- water Mysidae. 



KEY TO THE SPECIES OF INDIAN BRACKISH-WATER MYSIDAE. 



1. Both rami of the uropods divided by a transverse joint distal to the 

 centre. 



Thoracic legs without terminal brush of setae : dactylus not devel- 

 oped ; pleopods of the male well developed, exopod of the second 

 pair very elongated, rami of the third, fourth and fifth pairs 

 subequal. 



Telson entire, apex armed with four strong stout serrate spines : 

 distal half of the lateral margins armed with about fifteen 

 spines : antennal scale as long as the antennular peduncle 

 with the outer margin entire (i e., without setae) and terminat- 

 ing in a spine, six times as long as broad : carapace very 

 short : eyes large, black, on prominent stalks : eighth thoracic 

 limb in both sexes with the endopod reduced and papi.lli- 

 form .. .. .. .. Rhopalophthalmus egregius, Hansen. 



2. Both of the uropods undivided. 



(a) Outer margin of the exopod of the uropods armed with more 

 or fewer spines, but without setae between the spines and the 

 base : third pair of pleopods of the male with the exopod 

 elongated : first abdominal segment of the female with a pair 

 of lateral lamellae : telson long, as compared with the uro- 

 pods, cleft at the apex, the cleft armed with sharp serrations. 



Lateral margins of the telson armed with about fourteen 

 spines : no spine on the dorsal surface of the fifth seg- 

 ment of the pleon : posterior dorsal margin of the cara- 

 pace with a fringe of from six to nine slender processes : 

 exopod of the third pleopod of the male as described in 

 this paper . . . . . . . . Gastrosaccus muticus, W.M.T. 



(b) Outer margin of the exopod of the uropods setose, without 



spines : first abdominal segment of the female without lateral 

 lamellae : telson short, entire, without apical cleft. 



(c) Apex of the telson between the terminal spines of the lateral 

 margins truncate, armed with numerous short spines : first, 

 second and third pleopods of the male rudimentary as in the 

 female, exopod of the fourth pair elongate : antennal scale 

 setose all round. 



(1) Antennal scale two-jointed, about seven times as long 

 as broad ; lateral margin of the telson armed with 7-10 

 spines, apex with 12-17 spines not much shorter than 



the terminal spine of the lateral margin . . Potamomysis assimilis, W.M.T. 



(2) Antennal scale unjointed, about 4! times as long as 



