36 Memoirs of the Indian Museum. [Vol. II, 



Skin tough. The head, back and base of tail are covered with closely set, flat or nearly 

 flat denticles, usually with three or more enlarged tubercles in the scapular 

 region. The tail is covered for the greater part of its length with small spiny 

 denticles, which also occur scattered on the cutaneous flap. 

 Mouth. — The jaws are bent almost angularly, this being particularly noticeable as 

 regards the upper jaw, in the middle of which the teeth are smaller than they are 

 elsewhere. The middle part of the upper jaw is deeply concave from below. The 

 teeth are white ; their surface is nearly smooth and the transverse ridge is practi- 

 cally obsolete. Where they are quite unworn, however, it is possible to see that 

 the surface is divided into two areas ; a posterior one, of which the outline is 

 rounded and the surface obscurely sculptured, and an anterior one with an angular 

 outline and marked with distinct longitudinal grooves. On the floor of the mouth 

 there are three long slender processes situated close together in the middle, and 

 another near each angle. 



This species represents the genus Hypolophus of Müller and Henle and is certainly 

 very distinct from any other. I am doubtful as to the necessity for recognizing sub- 

 genera in the fishes, otherwise I would certainly recognize Müller and Henle' s name as 

 that of a sub-genus. 



There are several small specimens in spirit in the collection of the Indian Museum, 

 but the only fresh one that I have seen was a male measuring 151 '8 cm. across the 

 disk which was taken by the ' ' Golden Crown ' ' in August off the Burmese coast. 

 This specimen exhibited an interesting abnormality, lacking the distal part of the 

 tail completely. The cutaneous flap ran to the extreme tip, becoming gradually 

 lower towards this point. The tail, however, was no longer than the disk, and I have 

 little doubt that it had been accidentally abbreviated, although the wound had com- 

 pletely healed without even leaving a scar at the tip. A photograph of this speci- 

 men is reproduced on plate v, fig. i. 



Genus Urogymnus, MuUer and Henle. 



Tail very distinct from the disk, without a serrated spine. Disk stout, elliptical or sub- 

 circular. Teeth flattened, without a distinct transverse ridge but with the inner 

 margin raised. Other characters as in Trygon. 



Hitherto only one species of the genus has been known, namely Urogymnus as- 

 perrimus (Bloch and Schneider), but a second is here described. Unfortunately I have 

 only seen one fresh individual of the former, which was mutilated, and have not been 

 able to examine the latter except as a stuffed museum, specimen. The differences, 

 however, are so very clearly marked that I do not hesitate to describe the new species. 

 The two species may be distinguished as follows : — 



A. Pectoral fins covered with spiny denticles which have 



flat circular bases . . . . . . . . U. asperrimus, 



B. Pectoral fins covered with small rounded denticles, 



which at the periphery are almost granular . . U. lœvior. 



