1909.] N. Annandale : Report on the Batoidei. 17 



Family TRYGONID^ (Sting-Rays and Butterfly Rays). 

 Head and body forming a rhombic or subcrcular disk ; pectoral fins meeting in front 

 of the snout ; tail quite distinct. Tail without longitudinal folds, sometimes 

 with dorsal and ventral cutaneous, rayless flaps ; dorsal fins absent or very 

 small, a recumbent serrated spine usually present on the tail. No electric organ. 

 Of the true rays this family is the best represented in the Indian seas, in which 

 it is practically confined to shallow water. Four genera and twelve species are re- 

 corded by Day; to these, seven species are here added, one having recently been 

 described and three being described below for the first time, while three were pre- 

 viously known but had not been found (or recognized) in Indian seas. One of the 

 forms regarded by Day as distinct is here regarded as svnonymous with another. 

 Fifteen species have been taken by the ' ' Golden Crown." 



The Trygonidae , although their flesh is coarse, are eaten b}^ many castes of Indians, 

 who attribute to them certain tonic and aphrodisiac qualities. The tails of the larger 

 species are made into whips and walking. sticks, and there is no doubt that an extremely 

 valuable oil could be manufactured out of their livers (see Mr. Hooper's analysis, />os^e«). 

 The fishery or estuarine species in the river Hughli, however, which is referred to by 

 Blyth {Journ. Asiat. Soc. Bengal, xxix, p. 35, i860) , appears to have completely died out. 

 The five Indian genera may be distinguished as follows : — 



Key to the Indian Genera of Trygonidœ. 

 I. Tail with a serrated spine, without cutaneous folds or with them rudimentary 

 and not reaching the tip. Teeth flattened, with a transverse ridge or (rarely) 

 with a sharp cusp ; jaws not angular . . . . Trygon. 



II. Tail with a serrated spine, with a cutaneous fold several times as deep as itself 

 but not extending normally to the tip. Teeth flat, without a transverse ridge; 

 jaws angularly bent . . . . . . . . Hypolophus. 



III. Tail without a serrated spine. Teeth without a definite transverse ridge 



Urogymnus. 



IV. Tail with a serrated spine and a cutaneous fold extending to the tip Tœniuva. 

 V. Disc very broad and short, angular. Tail feeble, with or without a small dorsal 



fin, normally with a serrated spine. Teeth saddle-shaped, with one or m.ore 

 sharp cusps in front . . . . . . . . Pteroplatea. 



The first four genera in this key are very near one another and should perhaps be 

 regarded as subgenera. In Trygon the serrated spine is occasionally absent, while in 

 Hypolophus individuals occur in which, probably owing to injury in early life, the 

 cutaneous fold extends to the extremity of the tail. 



In diagnosing the species of this family it is particularly important that attention 

 should be paid to fresh specimens. Man}^ species grow to so large a size that it is 

 practically impossible to preserve them in alcohol, while the characteristic markings 

 disappear and the natural proportions are distorted in stuffed skins. 



With reference to measurements it is necessary that an exact statement should 

 be made as regards the methods adopted, for there are several different ways in which 



