ON THE BONES OF THE RHINOCEROS, 419 



noid facette is transverse, a little concave, not limited posteriorly, except 

 on the inner side, by a large process of the temporal bone, of which we 

 have spoken already, placed beneath the foramen auditorium, and which 

 is much more prominent than the tubercle placed behind this foramen, 

 and even than the mastoid process of the occipital bone. The foramen 

 auditorium sinks horizontally behind the posterior base of the arch. 



The foramen analogous to the spheno- palatine opens near the fifth 

 molar tooth in the palatine ; that corresponding to the pterygo-palatine, 

 a little more posteriorly over the union of the palatine and maxillary. 



The anterior orbital foramen is small, as is the foramen opticum ; 

 but the spheno-orbital, which comprises also the foramen rotundum, 

 and is concealed behind a ridge of the bone, is large. 



There is a vidian foramen at the base of the ala. The foramen ovale 

 •is confounded with the foramen lacerum. 



2. The Teeth. 



Independently of the importance of the teeth in general, in order to 

 attain a knowledge of the nature of animals, and particularly for the 

 determination of fossil animals, we must necessarily enter into some 

 detail regarding the teeth of the rhinoceros, because the late M. Faujas, 

 in his Treatise on Geology, has endeavoured to perplex this subject. 

 We shall first answer his remarks*. 



All rhinoceroses have seven molar teeth on each side, above and 

 below ; twenty-eight in all. 



A head of a two-horned rhinoceros in our Museum exhibits, to be 

 sure, but twenty that are apparent (plate 40, figs. 1 and 2), by reason 

 of the youth of the animal to which they belong ; but anatomists are 

 not deceived in cases of this kind, because they know how to find in 

 the sockets of the jaw bones the germs of the teeth which have not 

 yet appeared ; and these germs existed accordingly in this head, 

 which would have had twenty-eight, as all those of its species, if the 

 animal had not been killed too young. 



The head of the adult skeleton of the two-horned rhinoceros which 

 was brought hither some little time ago, has twenty-eight molar teeth, 

 precisely as all the others. (See plate 56, fig. 2). 



The skeleton of a one-horned rhinoceros, which forms the principal 

 object of our present description, exhibits, on one side of its lower jaw, 

 six teeth or stumps of teeth, and on the other (plate 40, fig. 4) the ap- 

 pearance of seven ; but that is a slight illusion, which cannot deceive 

 those who have studied the growth of teeth. 



All herbivorous animals, to commence with the horse, vise their 

 teeth to the root, because in proportion as the crown diminishes by 

 trituration, the alveolus becomes filled and forces the root out. When 

 this root consists of two branches, as in the rhinoceros, and the stock 

 of the tooth has been entirely worn, there remain two stumps of root : 

 these stumps fall one after the other, constantly diminished by tritu- 

 ration, and pushed out by the growth of the bone within the alveolus. 

 At last the alveoli themselves are entirely effaced. 



* Faujas, Essai de Geologie, t. i, pp. 193 — 196. 



