360 Dr. J. E, Gray on the Dentition of Rhinoceroses. 



pecially as some zoologists who admit the difference of the 

 two species refer R. Orossii^ of which we know nothing but 

 the horn, to each of the species. 



Ceratorhinus BlytMi. 



Mr. Blyth, in the ' Journal of the Asiatic Society of Bengal/ 

 vol. xxxi. t. iii. f. 1, 2, 3, lithographs from photographs (which 

 he has since given to me) three skulls of what he calls R. suma- 

 tranus from Tenasserim. 



These skulls, according to the photographs, differ so much 

 from each other that they do not afford materials for the de- 

 termination of the question of the species to which the Tenas- 

 serim Rhinoceros should be referred. 



The photographs represent the skulls of animals of very 

 different ages ; but I cannot believe the difference between 

 them depends solely on age, as the skull of the oldest (fig. 1) 

 and of the youngest (fig. 3) agree in the shape of the occiput 

 and in the upper surface not being produced behind, while tlie 

 skull of the half-grown one (fig. 2) has the upper surface of 

 the occiput very much produced backwards, and the occipital 

 condyles not so prominent. 



The three photographs are nearly of the same breadth at the 

 lateral condyles ; but the length of the upper surface of the 

 skull differs considerably as compared with its breadth. Thus 

 in the photograph of the aged specimen (t. iii. f. 1) the length 

 of the skull is once and three-fourths its breadth ; in the 

 youngest skull (t. iii. f. 3) it is very nearly of the same 

 proportion ; but in the nearly adult skull the photograph 

 represents the upper surface as a little more than twice as long 

 as the breadth at the condyles. 



The most striking difference is in the height of the occipital 

 end and the form of the lower jaw in the photographs of the 

 adult and nearly adult skulls (f. 1 & 2). 



In the adult skull the occipital end is high (that is, as high 

 as two thirds the length of the skull from the occipital condyle 

 to the end of the nose), and the hinder end of tlie lower jaw is 

 nearly erect, with a broad rounded lower part, which is promi- 

 nent, with diverging ridges on its outer margin. In the nearly 

 adult specimen the hinder end is not nearly so high compared 

 with the length, and the hinder end of the lower jaw shelves 

 off towards its lower edge and has not the expanded rounded 

 form of the lower jaw of the other specimen ; but it is curious 

 that the skull of the youngest one has the form of the occiput 

 of the very aged one and the form of the lower jaw of the 

 middle-aged one. All this shows the difficulty of distinguishing 

 the species of these animals and the necessity of waiting until 



