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



1 or 2 feet over the hard sand near the mouth of the lake. At the time when they 

 were obtained the water in the outer channel was as salt as that of the sea outside 

 the lake. In September 1914, when it was quite fresh we searched carefully for the 

 species in the same place, but were unable to discover any more specimens. The 

 species appears to be only a casual visitor to the extreme outer parts of the lake 

 during the salt-water season. 



The type specimens bear the no. 8970/10 in the Museum register. 



Family PALAEMONIDAE. 



Borradaile in a short preliminary paper, recently published l , has divided the 

 Palaemonidae into four sub-families, the Desmocaridinae, Pontoniinae, Palaemoninae 

 and Typhlocaridinae. The characters used in the separation of the first three of 

 these subfamilies are, in the main, those to which Sollaud has already drawn atten- 

 tion. I am inclined to think that the arrangement suggested is not likely to be 

 permanent ; but the number of forms obtained in the Chilka Lake is so small that 

 the occasion is not a suitable one for a discussion of the matter. 



The Palaemonidae found in the lake comprise seven species belonging to the 

 genera Palaemon, Leander, Urocaris and Periclimenes. The last two genera are 

 represented by single species which are described as new ; they are able to live in 

 either fresh or salt water and to tolerate considerable periodic variations in salinity. 

 Both species occur among weeds and Urocaris is one of the commonest and most 

 widely distributed Crustacea in all parts of the lake: the Periclimenes is found only 

 in the outer channel. 



The single species of Leander and one of the Palaemons, P. scabriculus , must be 

 regarded as casual visitors to the lake, the former from the sea, the latter from the 

 ponds or rice fields. 



Only females of Palaemon malcolmsoni and P. lamarrei have been found in the 

 lake and our observations lead us to conclude that these species visit its waters only 

 for breeding purposes. This is also the case with the remaining species of the genus, 

 P. rudis, the males of which accompany the females at this period. Adults of these 

 three forms do not live in water as salt as that of the Bay of Bengal ; but the young 

 of P. rudis were found in the outer channel at the salt-water season, while adults of 

 P. lamarrei are able to tolerate a considerable degree of salinity. P. malcolmsoni was 

 found only in fresh water. 



Although the species of Periclimenes and Urocaris are here described as new, 

 they also occur at other places on the east coast of India, the Periclimenes at the 

 mouth of the Adyar river at Madras, the Urocaris in backwaters in the same neigh- 

 bourhood and also in pure sea-water inside the coral reefs and in the shallows of the 

 Gulf of Manaar. The Urocaris is a very close ally of a species found in the Gulf of 

 California and on the Pacific Coast of Mexico. 



1 Borradaile, Ann. Mag. Nat. Hist. (8), XV, p. 206 (1915). 



