30 ORP]ODON. 



the skull resembles in its general form very much that of Anoplotherlum. The 

 upper outline of the skull forms an almost unbroken convexity from the inion to 

 the end of the nose; being depressed very slightly only upon the forehead at the 

 bifurcation of the sagittal crest. The outline of the inion is obliquely downward 

 and forward, and is only intruded upon by the occipital condyles. 



Among existing ruminants, the cranium proper of Ori'odon is very like that of the 

 Camel and Llama. As in these, the temporal fossa is large and extends superiorly to 

 the median line of the skull, where it rises upon a prominent sagittal crest, which 

 posteriorly, in conjunction with the occiput, forms an eminence jDrojecting above the 

 inion and constituting its summit. The fossa at the margin of the inion forms an 

 oblique crest, which relatively is not as deep as that of the Camel, and which is 

 constituted by the juiaction of the squamous portion of the temporal bone with an 

 elongated process from the pars petrosa intercalated between the former and the 

 occiput; and above by the occiput alone. Anteriorly the fossa is bounded by the 

 divergent portion of the sagittal crest upon the post-orbital process. 



The temporal surface generally is smooth and convex, but is concave along the 

 course of the occipital crest and the sagittal crest posteriorly, and as in the Camel, 

 nearly one-half of its extent is constituted by the squamous portion of the tem- 

 poral bone. 



Following the course of the squamous suture at its anterior part, in some of the 

 crania, the parietal bone is depressed into a groove, resembling the impression 

 of a bloodvessel, or the trochlea of a tendon ; but in other specimens this groove 

 does not exist, or is very slight. At the back part of the same suture, varying in 

 position in different individuals, are one or two vascular foramina, directed upward 

 and backward. (V. 1.) 



In all the specimens under investigation the zygomatic arch is broken ; but, 

 judging from a portion remaining in the skull of an immature animal, it is rela- 

 tively as strong as in the Camel. (VI. G.) 



The malar bone, as in the Deer, has a much more anterior position than in the 

 Camel, but it is more robust than in this, and its outer surface is convex and on 

 the same plane with the entrance of the orbit, being directed forward and upward. 

 Anteriorly, it is continuous with a corresponding swell of the face, converging 

 forward above the alveolar processes. 



The post^orbital process of the os frontis combines with that of the malar bone, 

 so as to form a complete post-orbital arch, such as exists in all recent ruminants ; 

 which is relatively stronger than that of the Deer, Ox, or Sheep, but is not quite 

 as strong as in the Camel. (IV. 3; VI. 4, 6.) The temporal attachment extends 

 upon the post-orbital arch, as far as the transverse suture. 



The entrance of the orbit is sub-rotund, and is directed to about the same extent 

 forward as in the Deer, but in a slight degree more upward. (IV. 3.) 



The face, in its general form, strongly resembles that of Anophtherium ; and 

 in comparison with that of the Deer, not only appears to be shortened to an extent 

 corresponding with the vast hiatus existing anterior to the molars in the latter, but 

 also to recede; for, the last molar is on a line vertical to the post-orbital arch, as 



