I909.J 



N. Annandai^e : Report on the Batoidei. 



23 



tip of the snout ; while in the adult this point is situated at nearly four-fifths of 

 the distance. All the proportions of the disk, however, are variable. The angle of 

 the snout is rather variable but in fresh specimens it is, as a rule, slightly less than 

 a right angle; in the unborn young it is, at any rate in some specimens, obtuse. 

 The length of the snout, measured from the eyes, is about I of the total length of 

 the disk in the adult and between ^ and J in the young. The outline of the front of 

 the disk is somewhat sinuous in the adult but forms almost a simple concave 

 curve in the young. 



Fig. 2. — Diagram showing the difference in outline between the young (A) and the adult (B) of 



Trygon uarnak. 



Eyes large and prominent, especially in the young. The dorsal wall of the spiracle 

 forming a convex longitudinal flap. 



Tail ' more than twice as long as the disk, cylindrical, tapering, armed with a single 

 rather slender serrated spine, which is situated much nearer the base than the 

 tip of the tail. No cutaneous folds above or below. 



Skin tough. In the young there are as a rule several relatively large rounded 

 tubercles in the mid-line of the scapular region, and these, although at first 

 they are sometimes practically alone, are usually surrounded by smaller, heart- 

 shaped, nearly flat denticles which have the narrower end pointing backwards. 

 In the adult the middle of the back is somewhat sparsely covered with similar 

 but relatively smaller denticles, with which are interspersed numerous small, 

 spiny ones with stellate bases. These become more numerous on the posterior 

 part of the disk and the base of the tail, which is completely surrounded by little 

 almost granular denticles with the spiny denticles scattered among them. This 

 arrangement is continued for the whole length of the tail. There are no denticles 

 on the periphery of the disk or on the ventral surface, but those on the back do 



' In a large proportion of the larger specimens of the genus Trygon the tail i 

 difficult to tell whether mutilation has occurred or not. 



mutilated ; it is often 



