ON THE BONES OF THE RHINOCEROS. 417 



towards its base, in order to produce a projecting plate behind the 

 foramen of the ear and the posterior base of the zygomatic arch. 



The line of the base presents towards its middle the condyles, and 

 at the sides the mastoid processes, pointed and hooked ; in the hog these 

 processes are precisely under the occipital condyles. 



In front of each of these processes there is another very large one, 

 which belongs to the temporal bone, and which contributes to the 

 formation of the articulation of the jaw; it prevents it from moving 

 much from right to left, and corresponds with a fissure situated at the 

 inner extremity of the maxillary condyle. 



Between these two processes, but a little more interior, is another 

 short process, the end of which is hollow, and receives the styloid 

 bone. 



The impressions of the muscles divide the occipital or posterior 

 surface of the pyramid into four fossae. The anterior surface descends, 

 whilst it widens as far as between the eyes, where the post-orbitar 

 processes of the frontal bone are its most widely separated limits. It 

 becomes narrow without terminating completely in a point, because 

 the two temporal ridges do not unite even in the old animals, and 

 they go each separately to join the occipital ridge. The point of the 

 nose completes the formation of the rhomboid which characterises the 

 upper surface of the entire cranium. The region between the eyes is 

 concave in the longitudinal direction, and plane in the transverse ; 

 that of the bones of the nose is convex in every direction. 



The parietal bones commence a little before the summit of the py- 

 ramid ; they terminate towards the middle of the space between this 

 crest and the orbital processes. The frontal bones terminate a little 

 before the processes, by uniting to the bones of the nose by a transverse 

 suture, which passes from one lachrymal to the other. Their suture with 

 the maxillary bones sets out from the same point, where the preceding 

 meets the lachrymal. The sutures corresponding to the coronal and 

 lambdoid are perfectly transverse. This latter is anterior to the occi- 

 pital ridge. 



The squamous suture, or the limit of the parietal and temporal, in 

 the fossa of this latter name, is parallel to the direction of the anterior 

 surface of the pyramid. The great ala of the sphenoid bone ascends 

 but a very little way into the temporal fossa, and this bone does not 

 articulate with the parietal. The palatine bone ascends therein by a 

 very narrow slip, and then goes forwards towards the lachrymal bone, 

 by a slip, which is also very narrow. 



The lachrymal bone advances more over the cheek than into the orbit, 

 and has a hook at the edge of the orbit, behind which is the foramen. 

 The frontal bone has scarcely any post orbital projection. 



More than half the zygomatic arch behind belongs to the temporal 

 bone ; all the remainder belongs to the malar bone. 



The malar bone passes over the cheek, where it is articulated with 

 the lachrymal. 



The direction of the arch is like an Italian S, descending obliquely 

 from behind forwards : its lower edge is very thick and very projecting. 

 There is a very slight inferior postorbital prominence, in the formation 



