TRYGONIDJE. 



49 



Hob. Bed Sea, east coast of Africa, seas of India to the 

 Malay Archipelago. One, 2 feet across the disk, existed in the 

 Madras Museum. This species is said to attain to 4 or 5 feet in 

 length. 



Fig. 20. Uroyymnus asperrimus. 



2. Genus TRYGON, Adanson. 



Syn. Himantura, Hcmitrygon, and Hypolophus, Miill. & Henle ; Para- 

 tryyon, Duineril. 

 Pdkat, Marathi. 



Disk oval or rhomboidal ; tail elongated and tapering. Nasal 

 valves coalescent, forming a quadrangular flap. Teeth flattened, 

 or with a central point or transverse ridge. Pectoral fins united an- 

 teriorly ; tail destitute of a fin, or if with a cutaneous fold, such 

 does not extend to its extremity ; it is armed superiorly with one 

 or two lanceolate spines that are serrated on both sides. Body 

 smooth or with tubercles. 



In this genus the colours in individuals of the same species are 

 subject to considerable variation, and this is not invariably due to 

 age. The character of the tubercles and their extent have also 

 been (as I think erroneously) employed to characterize some 

 species : thus one, Trygon chindrnkee (Cuv.), Bleeker, is a form 

 without tubercles or spines, except on the tail; T. polylepis, 

 Blt-ckcr, has small tubercles in the interorbital space, a narrow 

 band along the back with a few indistinct enlarged ones, but none 



