988 THE OSTEOLOGY OF ELOTHERIUM. 
hemispheres were conyoluted, but the conyolutions are so feebly marked that they are 
hardly worth description. It is obvious, howeyer, that the gyri were fewer and simpler 
than in any of the modern ungulates. 
The 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 great. This breadth is still further reduced by the 
relatively very large size of the periotic bones which extend freely into the fossa. 
IV. THe VERTEBRAL CoLumy. 
The vertebral formula is: C 7, Th ? 138, L. 6,S 2, Cd 15 -+ 
The atlas (Pl. X VIII, Fig. 3) is very wide transversely, and at the same time it is of 
considerable antero-posterior extent, a shape which recalls that of Anoplotherium, 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, but is much less strongly developed. The articular surfaces for 
the axis are low and broad, and haye 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 yery slightly concave and are surrounded by prominent 
borders. The facet for the odontoid is wide, and deeply conecaye in the transverse direc- 
tion, but 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 
