378 OK THE FOSSIL BONES OF rACHYDEUMATOUS QUADRXTPEDSv 



in this it proceeds outwards as it goes back. Its most prominent part, 

 (fjf), is almost opposite to the articulation of the jaw. 



The suture which distinguishes the apophysis of the temporal from 

 the jugal bone, descends obliquel)^, backwards from the post orbi- 

 tar apophysis of the latter, to the articulation of the jaw (see d e, 

 fig. 1, plate 31). As the temporal fossa is very deep, the distance be- 

 tween the skull and the arch [e h, plate 31, figs. 2, and 3) is somewhat 

 greater than the size of the skull, (e e, ib.) 



The hole of the ear is exceedingly small, and placed quite behind the 

 upper edge of the arch. It gives birth to a long meatus, concealed in 

 the thickness of the bone. 



The bones of the nose are very long and narrow : they enlarge at 

 their base by a little point, which runs outwards between the frontal 

 and the lachrymal. 



The intermaxillary sutures re-ascend obliquely to one fourth of the 

 length of the bones of the nose. 



The suborbitar perforation is placed in the middle of the contracted 

 part of the muzzle, and is rather large. The external aperture of the 

 nostrils is vertical and almost round. It is only surrounded by the 

 nasal and incisive bones. 



The lower surface of the skull (plate 31, fig. 3) is remarkable for 

 the singular enlargement of the muzzle in front, principally formed 

 by the sockets of the canines, and owing to the two series of grinders 

 being either parallel, or rather a little apart in front. This latter cir- 

 cumstance is, I believe, unparalleled in any other living animal. 



The palate is very much slanted in front, u, between the incisive 

 bones. There is a double incisive hole, v v, and the suture sepa- 

 rating the incisive from the maxillary bone, next forms a strong 

 point backwards, w, occupying a fourth of the length of the palate. 

 The maxillary bone displays another great hole, at which the small 

 canal terminating at the other incisive hole at y, commences. It ap- 

 pears, in general, that the enormous lips of the hippopotamus required 

 thick nerves, for the passage of which these holes are perforated. The 

 palatine bones likewise advance in a sharp point as far as z, opposite 

 the interval between the fourth and fifth grinder. The posterior slope, 

 &c. corresponds with the termination of the series of teeth. The 

 sphenoid occupies but a small place in the pterygoid wing, which is 

 quite simple and almost entirely of the palatine bone. The pterygoid 

 bone prolongs the point of the wing into a little crotchet, x ; the bone 

 of the tympanum B p, is irregular, angular, not at all prominent, and 

 contains a cell communicating by a small hole with the real chest, 

 which is very small ; the mastoid apophysis is jDointed and short, and 

 belongs to the occi2:)ital. In general, the whole region of the os basi- 

 laire is small in proportion. 



The glenoid jDrocess of the temporal is slightly concave, and ex- 

 tends obliquely from the outside to the inside, and a little from top to 

 bottom towards the back. 



In the orbit, there are two upper orbitar holes, one corresponding 

 Avith the sphenoid and pterygoid palatine, a small- optic hole, a spheno- 

 orbitar hole which also embraces the circle, and an oval hole, which unites 



