4o8 



Memoirs of the Indian Museum. 



[Vol. V, 



small tubercles indefinitely scattered. In this species the denticles do not form as 

 definite a pattern as in Trygon gerrardi. The tail is provided with a single serrated 

 spine, and its dorsal and lateral surfaces are uniformly covered with denticles. The 

 cross- section of the tail anterior to the spine is distinctly flattened, which character 

 marks it off from allied species, in all of which the cross-section in that position is 

 circular. In a young male specimen the tail is more than three and a half times the 

 length of the disk, but in an adult female its length (perhaps mutilated) is only one 

 and a half times that of the disk. 



Colour : — The dorsal surface of the disk is dark olive-brown and the dorsal and 

 lateral surfaces of the tail are also brown without markings; the ventral surface 

 (including the base of the tail) is white suffused with pink. The measurements of 

 the four specimens in the collection are given below: — 





Adult cf , Nalbano, 

 Nov. 1914. 



Adult 9- , Balu- 

 gaon, 2-1-15. 



Adult ? , Balu- 

 gaon, 4-4-15. 



Young d 1 , Balu- 

 gaon, 5-1-15. 















mm. 



mm. 



mm. 



mm. 



Breadth of disk 



530 



582 



546 



198 



Length of disk 



512 



582 



538 



190 



Distance between the eyes . . 



68 



71 



66 



38 



Snout 



106 



127 



117 



43 



From the broadest part of the 

 disk to the end of the snout. 



215 



242 



221 



■ 

 68 



Breadth of mouth 



43 



51 



49 



17 



Distance between mouth and 

 vent 



317 



381 



320 



144 



Tail .. 



912 



Mutilated 



762 



594 



The adult female from Balugaon collected on the 2nd of February, 1915 is slightly 

 peculiar in the shape of the disk, the angle at the snout being somewhat obtuse; 

 its caudal spine is wanting but perhaps it was lost during life; the tail, which is very 

 short, must have been mutilated, and is, moreover, less flat than in the rest of the 

 specimens. 



This species is a permanent inhabitant of the main area, probably breeding in 

 the lake. 



Distribution : — R. Hughli, Bay of Bengal, Malay Archipelago. 



Trygon imbricata (Schneider). 



1801. Raia imbricata, Schneider, Bloch's Ichthyol., p. 366. 



1841. Trygon imbricata, Müller and Henle, Plagiost., p. 164. 



1841. Trygon walga, Müller and Henle, ibid., p. 159, pi. li, fig 1. 



1878. Trygon imbricata, Day, Fish. Ind., p. 739. 



