igog.] N. Annandale : Report on the Batoidci. 47 



and distinct from the trunk. Eyes about half as large as the spiracles, pro- 

 tuberant in life, separated by a concave interspace about half as long as 

 their distance from the anterior border of the disk. Margins of spiracles smooth. 



Mouth surrounded posteriorly by a semicircular fold, about half as wide as its 

 distance from the anterior border of the disk, provided with thick, tuberculate 

 lips, which are discontinuous in the middle of the anterior border. Teeth occupy- 

 ing nearly the whole of the mandibular surface, with a broad, bluntly pointed 

 transverse ridge. A bilobed, prong-like, vertical process on the roof of the mouth 

 and a similar one on the floor. Nasal flap with a distinct median longitudinal 

 groove and a median process on the free edge. 



Colour. — Dorsal surface dull chocolate colour with a purplish tinge. Ventral surface, 

 edge of disk and fins, a large oval spot on each side of the back some distance in 

 front of the posterior margin of the pelvic fins, and a forwardly directed streak 

 on each side of the anterior part of the tail, cream colour. 



This species exhibits much the same variation as Narcinc tinilci and A^. hruuncu in 

 respect to its fins. It has been taken by the ' ' Golden Crown ' ' in considerable 

 numbers off the Orissa coast and appears to be common all over the Bay in shallow 

 water. It is not so common as N. timlci and N. hrunnca , however, and perhaps 

 inhabits slightly deeper water. "" 



Large specimens measure 16 cm. in total length and 9 cm. across the disk. 



Genus Bengauchthys, gen. nov. 



Closely allied to Astrape, from which it is distinguished by its thick, fleshy disk, 

 rudimentary pectoral fins, and degenerate eyes. 



I think it well to separate a form represented by two individuals in the ' ' Golden 

 Crown ' ' collection from Astrape as a distinct genus, in order to emphasize the peculiar 

 manner in which this form has become adapted for a more or less sedentary existence. 

 In several respects the adaptation is of a nature closely similar to that which has brought 

 about the evolution of Benthobatis from Narcinc, although the environment in which 

 this evolution has taken place is not the same in the two cases. Benthobatis, as I have 

 already pointed out, is a deep-sea form — it occurs at depths from about 400 to about 

 700 fathoms — and, like many deep-sea forms, has degenerate eyes. The disk, moreover, 

 is thick and muscular and bears on the dorsal surface numerous little glandular pits ; 

 the pectoral fins are not clearly marked oft' from the body. In all of these points the 

 species of Bengalichthys to be described immediately resembles Benthobatis, although 

 it is not a deep-sea form, having been taken in only 15 fathoms. In two striking 

 characters, however, it dift'ers from Benthobatis, viz., in coloration and in the number 

 of the dorsal fins. The former dift'erence is probably due to its environment, the latter 

 to its ancestry ; in other words, the former is an adaptive character, the latter a 

 morphological one. A character common among deep-sea fish of all kinds is a dark and 

 uniform coloration of both the dorsal and the ventral surface, while among the rays of 

 shallowwater it is unusual for the ventral surface to be dark, although this is the case 



