78 ON THE EXTINCT MAMMALIA OF 



relation to the Lateral borders of the inioii that they do in recent ruminants. The 

 basi-occipital articulates with the basi-sphenoid on a line with the post-glenoid 

 tubercles. 



The squamosal, as in the Camel, contributes largely to the temporal surface of the 

 cranium. The mastoid is seen, as in the Deer, as a narrow fusiform bone intercalated 

 between the squamosal with its post-auricular process and the ex-occipital. 



The mastoid process is almost obsolete, being smaller than the post-auricular 

 process, between which and the paramastoid process it occupies a small angular 

 interval. 



As in all ruminant and suilline animals, there is a single symmetrical parietal, 

 which, as in the Camel family, is very long compared with its condition in ordinary 

 ruminants. It is narrow behind, and gradually widens to the fore part of the 

 squamosals, where it sends downward a prolongation to join the ali-sphenoids In 

 front it usually is more or less deeply notched to receive a triangular point of the 

 frontals. In some skulls the front border forms a wide angular shallow notch ; and 

 in others it is nearly straight or transverse in its course. 



The frontal bones are usually found separated as in recent ruminants, and this is 

 also the case in old skulls, but occasional specimens are seen in which the two bones 

 are co-ossified at the posterior angular extremity. They contribute a small portion 

 of surface to the temporal fossae, just back of the orbits. They converge regularly 

 from the post-orbital arches to the anterior angular processes, which are long, tri- 

 angular and pointed, and which reach some distance in advance of the lachrymal 

 bones. A deep notch between the angular processes receives the posterior extremi- 

 ties of the nasal bones. 



The post-orbital arch receives about an equal contribution from the frontal and 

 malar bones. 



In the formation of the zygoma the malar bone is deeply notched from behind 

 forward to receive the end of the zygomatic process of the squamosal. The lower 

 arm of the notch, sustaining the end of the latter process, is bent slightly downward 

 in its backward course, and is much longer than the upper arm. 



The lachrymal bone forms two sides of an irregular cube, and the margin of union 

 of the two sides is produced into the comparatively large lachrymal tubercle. The 

 facial surface of the bone is in great part depressed to form the deep hemispherical 

 lachrymal fossa. 



As in recent ruminants, the lachrymal bone articulates with the frontal, maxillary, 

 malar and palate bones, but is separated some distance from the nasal by the advance 

 of the angular process of the frontal bone. 



The nasal bones are of nearly uniform breadth, except at their converging ex- 

 tremities. They are usually slightly conve'x both transversely and in the length, but 



