1909.] 
17 
N. Annandale : Report on the Batoidei. 
Family TRYGONIDÆ (Sting-Rays and Butterfly Rays). 
Head and body forming a rhombic or subc’rcular 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 Trygonidæ, although their flesh is coarse, are eaten by 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/ea). 
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 Trygonidæ. 
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 Tæniura. 
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 more 
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, w’hile 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. Many 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 
