168 SKELETON OF THE KHINOCEROS. 



by tlie rhinoceros. Botli scapulte and iliac bones are of 

 greater breadth, and less length. The nlna is fully de- 

 veloped in the fore-limb, and the fibula in the hind-leg; 

 but there is no power of rotation of the fore-limb in any 

 hoofed quadruped. The upper surface of the skull is 

 roughened for the attachment of the horn, and in two 

 distinct places where the species has two horns. 



If the equine skull be compared with that of the rhi- 

 noceros, the basioccipital will be seen to be narrow and 

 more convex. The true mastoid intervenes, as a tuberous 

 process, between the post-tympanic and par occipital pro- 

 cess, clearly indicating the true nature of the post-tym- 

 panic in the rhinoceros ; the tapir shows an intermediate 

 condition of the mastoid between the rhinoceros and 

 horse. The latter differs from both the tapir and rhi- 

 noceros in the outward production of the sharp roof of 

 the orbit and the completion of the bony frame of that 

 cavity behind by the junction of the postorbital process 

 with the zygoma. The temporal fossa, so defined, is small 

 in proportion to the length of the skull: the base of the 

 postorbital process is perforated by a superorbital fora- 

 men. The lachrymal canal begins by a single foramen. 

 The premaxillaries extend to the nasals, and shut out 

 the raaxillaries from the anterior aperture of the nos- 

 trils. The chief marks of afiinity to other odd-toed 

 hoofed beasts {Penssodactyles) are seen in the shape, size, 

 and formation of the posterior aperture of the nostrils, 

 the major part of which is bounded by the palatine bones, 

 of which only a small portion enters into the formation 

 of thife bony palace, which terminates behind opposite the 

 interspace between the penultimate and last molars. A 

 narrow groove divides the palato-pterygoid process from 

 the socket of the last molar, as in the tapir and rhinoceros. 

 The pterygoid process has but little antero-posterior ex- 



