Memoirs of the Indian Musenni. 
10 
[Voi.. II, 
characters, which are discussed below. I cannot regard it as generically distinct from 
its allies usually placed in RhinohaUis . 
The two Indian genera recognized in this paper are, therefore, Rhamphobatis , 
Gill (t86i), and Rhinobatis , Bloch and Schneider (i8oi). 
Genus Rhaj\iphobatis, Gill. 
Head rounded in front, not produced into a rostrum. Back bearing large comxjressed 
bony tubercles arranged in rows. Teeth lozenge-shaped, transverse, with man}" 
sinuous, parallel transverse ridges. 
I have made a careful comparison between the skull of the one species of this 
genus and that of Rhinobatis djeddensis. The cranial cartilages are somewhat different 
in the two species. In the latter a single rostral cartilage projects forward between the 
nasal capsules ; its ventral surface is hard, solid and undivided, but there is a broad 
and lengthy longitudinal depression on the dorsal surface. In Rhamphobatis , on the 
other hand, a pair of rostral cartilages, which are much broader and flatter than the 
single one in Rhinobatis and onl}^ joined to one another at the base by membrane, 
arise in the same position and only unite as cartilages near the tip of the snout. The 
condition in Rhinobatis granulatns , R. schlegelii and R. halavi is exactly the same as 
in R. djeddensis. 
There is, moreover, a distinct difference between the teeth of Rhamphobatis and 
those of all the species of Rhinobatis I have examined. In the latter genus, although 
the teeth differ considerably in the different species, they may be described in all cases 
as having a single transverse ridge, which sometimes is raised in the centre so as to 
be almost conical. In Rhamphobatis , on the other hand, the teeth bear numerous 
wavy transverse ridges, none of which is much better developed than the others. 
Rhamphobatis ancylostomus (Bloch and Schneider). (PI. v, fig. 5.) 
Pectoral fins with the anterior margins not joined by skin to the sides of the head. A 
median dorsal ridge of large, compressed, irregular tubercles running from just 
behind the spiracles a little more than half way to the first dorsal fin ; a similar 
ridge on either side running along the internal margin of the orbit and spiracle and 
continued in a somewhat less conspicuous fashion roimd the anterior margin of the 
former; a patch of similar tubercles in front of each of these lateral ridges, which 
are continued posteriorly, after a considerable interruption, by short and feeble 
ridges in a straight line with them ; a still shorter and feebler outer lateral ridge 
on either side parallel to the main one. The two dorsals and the caudal fin 
about equidistant from one another ; the posterior rather smaller than the an- 
terior ; the lower lobe of the caudal long and pointed. A strong ridge on the 
side of the tail. Mouth strongly imdulated, the two downward projections on 
the upper jaw and the three upward projections on the lower jaw approximately 
equal ; the teeth lozenge-shaped, the breadth f — y of the length ; ten distinct 
ridges on the unworn teeth; teeth much smaller on the excavations of the jaw, 
than on the projections. 
