288 THE OSTEOLOGY OF ELOTHEKIVM. 



hemispheres were convoluted, but the convolutions are so feebly marked that they are 

 hardly worth description. It is obvious, however, that the gyri were fewer and simpler 

 tban in any of tbe modern ungulates. 



Tbe cerebellum is rather small, though the cerebellar fossa has a vertical diameter 

 not much less than that of the cerebral fossa. Antero-posteriorly the former is quite 

 short and its transverse breadth is not oreat. This breadth is still further reduced by the 

 relatively very large size of the periotic bones which extend freely into the fossa. 



IV. The A'ertebeal Column. 



The vertebral formula is : C 7, Th ? 13, L 6, S 2, Cd 15 + 



The atlas (PL XVIII, Fig. 3) is very wide transversely, and at the same time it is of 

 considerable antero-posterior extent, a shape which recalls that of Anojplotherium, rather 

 than that of the recent ruminants or suillines. The anterior cavities for the occipital 

 condyles are deep and wide, but low and depressed. Dorsally, these cotyles are widely 

 separated by a broad,- but not very deep emargination of the neural arch, nor do they 

 approximate each other very closely on the ventral side, a notch of considerable width 

 intervening between them at this point. The neural arch is thick and heavy, but short 

 from before backward and quite narrow transversely ; it is also low, not arching strongly 

 toward the dorsal side, and nearly smooth, being free from any but the most obscurely 

 marked ridges. The foramina perforating the arch for the first pair of spinal nerves are 

 unusually large. The neural spine is rudimentary and forms only an inconspicuous 

 tubercle. The neural canal is low and broad, forming a transversely directed ellipse. 

 The inferior arch is considerably more elongated antero-posteriorly than the neural, and 

 has but little transverse curvature, except laterally, where it rises to form the sides of 

 the neural canal. The hypapophysis is represented by a small, backwardly directed 

 tubercle, which arises from the hinder margin of the ventral arch, and occupies the same 

 position as in the pigs, hut is much less strongly developed. The articular surfaces for 

 the axis are low and broad, and have a very oblique position, presenting inward toward 

 the median line, almost as much as backward ; they have also a slight dorsal presenta- 

 tion. In shape, they are very slightly concave and are surrounded by prominent 

 borders. The facet for the odontoid is wide, and deeply concave in the transverse direc- 

 tion, hut quite short antero-posteriorly. This facet is connected at the sides with those 

 for the centrum of the axis, but distinct ridges are formed along the line of junction. 



The transverse processes of the atlas extend out widely from the sides of the arch, 

 attaining their greatest transverse breadth along the posterior line ; they are also very 

 long in the fore-and-aft direction, reaching far behind the surfaces for the axis. For 

 most of their course the transverse processes have thin borders, but posteriorly the 



