A Memoirs oj the Indian Museum. [Vol. HI, 



On the same voyage as that on which the large individual was taken, a young 

 one^ perhaps born from it prematurely, was also captured. It differed from the 

 adult in the total absence of scales from the pectoral fins and snout and in possessing 

 only blunt scales on the body and tail. Although there was no trace of a spine on 

 the latter, the place in which it would have been in a Trvgon was occupied by a 

 distinct naked groove (pi. ii, fig. i6)- an interesting piece of evidence as regards 

 the descent of Urogymnus from a genus such as Trygon with a poison-spine on 

 the tail. On the snout a few soft tubercles were visible, which appeared to be 

 developing spines with a flat base. 



Family MYLIOBATIDAE. 



Aetobatis narinari (Euphrasen). 



(Plate ii, fig. 2.) 



A. narinari, Mem. Ind. Mas., ii, p. 55 ( v ). 

 A. guttata, ihid., p. 56 ( s ). 



It becomes clear from an examination of specimens from localities outside the 

 Bay of Bengal and of individuals taken recently by the " Golden Crown " off the 

 Madras coast, that I was wrong in two particulars as regards the species of Aetobatis ; 

 firstly, in thinking that the form I called .4. narinari was peculiar to the Atlantic, 

 and secondly, in regarding it as specifically distinct from the common Indian form. 

 For some reason all the specimens I had examined in a fresh condition were males, 

 in which the snout appears to be normally more pointed than it is in females; 

 and it is evident that the coloration of the species is more variable than I 

 realized. In Edinburgh and London there are Indian specimens that agree closely 

 with American and vSouth .Sea specimens in the British Museum, while an old female 

 from the Madras coast differs in more respects than one from all other specimens I 

 have seen. It appears, however, that if very old and very young individuals, in 

 both of which the spots are obscure or absent , are omitted from consideration , three 

 colour varieties may be distinguished as follows : — 



Var. A. — Entire dorsal surface of disk, including the snout, spotted. 



Var. B. — Spots on the dorsal surface confined to the post-spiracular part of the 



disk. 

 Var. C. — Spots confluent into short transverse streaks. 



Var. B is the common variety in the northern parts of the Bay of Bengal, but is 

 by no means confined to Indian seas Var. A is found off the Coromandel and Mala- 

 bar coasts as well as in the Atlantic and South Pacific ; while var, C is probably 

 liable to occur in diverse places as an individual sport. 



The large female recently taken bj^ the "Golden Crown" is practically devoid 

 of spots, which appear to have become almost obsolete. Very young individuals 

 are also unspotted ; but in them the spots are just commencing to appear. For 

 the following measurements of the large specimen I am indebted to Dr. Jenkins 



