1915-] Fauna of the Chilka Lake : Mammals , Reptiles and Batrachians. 167 



would often rush in straight towards the rocks, as if about to land upon them, and on 

 one occasion we saw an individual strand itself on a flat shelf and remain for some 

 seconds with, its flippers and the forepart of its body practically out of the water. At 

 other times it swam along more slowly with its mouth open and the upper part of its 

 head exposed. In this case it was probably feeding on the shoals of small Crustacea 

 (Macropsis orientalis, Tattersall) that swarm along the edge of the rocks. 



Oldfield Thomas {op. cit., 1891) has given good reason for regarding the Irrawaddy 

 form of this genus (0. fluminalis, Anderson) as identical with the marine one and 

 Anderson's statement that it does not occur in the lower reaches of the river seems 

 to be based on insufficient evidence. The species is found in the Bay of Bengal, the 

 Straits of Malacca, Borneo and the Gulf of Siam. It ascends the Irrawaddy for hun- 

 dreds of miles and occurs in the Gangetic delta with Platanista gangetica, though it 

 apparently does not penetrate very far inland on the west side of the Bay of Bengal. 



REPTILES AND BATRACHIANS. 

 The following is a list of the reptiles and batrachians found in the Chilka 

 Lake : — 



Reptiua. 



OPHIDIA. CHELONIA. 



Chersydrus granulatus. Chelone imbricata. 



Cerberus rhynchops. Chelone my das. 



Hydrophis obscurus. Emyda granosa intermedia. 

 EMYDOSAURIA. 



Crocodilus palustris. 

 Gavialis gangeticus. 



Batrachia. 



Rana cyanophlyctis. 



The three snakes all belong to the family Colubridae, but to three different 

 groups of that great assemblage : Chersydrus granulatus to the Aglypha , Cerberus 

 rhynchops to the Opisthoglypha and Hydrophis obscurus to the Proteroglypha. As 

 all three are modified to a greater or less extent— Cerberus less than the others— for an 

 aquatic existence, and as the modifications are the same or tend in the same direc- 

 tion, the species afford an interesting instance of convergence. 



From a geographical point of view the three snakes have some interest. 

 Chersydrus granulatus, which is a true estuarine species sometimes found out at sea, 

 is widely distributed in the Malay Archipelago, but in Indian waters is apparently re- 

 stricted to the east coast of the Peninsular Area and the southern part of the Malabar 

 Zone. Cerberus rhynchops, which ascends rivers far higher than the limits of their 

 estuaries, has a similar general distribution, but is found in the Gangetic and other 

 Indian river-systems beyond the range of Chersydrus. Hydrophis obscurus is, so far 



