TETITIARY VEKTEI51UTA OF THE FATtM. 
i;32 
condyles. Its body is keeled ventrally and it unites with the basisphenoid at about 
tli(' level of the glenoid cavity for the mandible : the line of union with the hdsi- 
tiphenoid {hsp.) is marked by a fairly prominent trans\ erso ridge. The lateral border of 
lli(' median limb is separated from the anterior border of the lateral portion by a 
sbarj) notch, through which the hypoglossal nerve probably passed, there being, as 
in the later Troboscidea, no condylar foramen. 
With the possible exce])tion of a small portion of their inner ends, the whole of the 
occipital condyles are formed by the exoccipitals [exo.). The condyles themselves are 
much larger and project furtlier behind the skull than iii Elephas, in which their 
articular surface seems to look mainly downwards and to project very little beyond 
the rest of the exoccipital bones. Here, on the other hand, the condyles are so 
sharply marked off from the rest of the bone as to be almost pedunculate. Their 
articular surface extends far on to the dorsal surface, and they are very strongly convex 
from above downwards — in fact, roughly speaking, they may be said to form about 
twm-thirds of the surface of a cylinder — and at the same time they are slightly convex 
Irom side to side. From the form of the condyles, therefore, it would appear that the 
range of movement allowed to the skull in an up-and-down direction must have been 
very great, while that from side to side was comparatively restricted. 
The foramen magnum (fm.) is oval in outline and does not look downwards so 
much as in Ehphas, mainly owing to the fact that the posterior border of the basi- 
occipital is less deeply notched. Ventrally and laterally the surface of the exoccipitals 
runs forwards in a gentle curve to join the ])ost-tympanic flange {ptg.) of the squamosal. 
On the ventral surface near the union with the squamosal the exoccipital bears a blunt 
prominence {pp.), which is the only re[)reseutative of the paroccipital process, and is 
therefore homologous with the thin plate-like ventral process of the bone described 
in the skull of Moexitherium. The upper portion of the bone above the condyles and 
the foramen magnum slopes forwards, and the two elements meet in the middle 
line, separating the supraoccipital from the foramen magnum by a distance of about 
5 centimetres. 
The precise boundaries of the supraoccipital [soc.) are indistinct. In the middle 
line it, like the upper j)ortion of the exoccipitals, is inclined forwards ; above it is 
hollowed out by a great median fossa, the floor of which is greatly rougliened and is 
obscurely divided into halves by a sliglit median ridge. This fossa is one of the most 
characteristic peculiarities of the skull of the later Ele[)hants, but in l^alccom.astodon 
it is far more sharply defined, probably, for the most part, on account of the smaller 
development of the cellular tissue of the rest of the bone, d’he sides of the fossa are 
formed by broadly rounded vertical ridges. The superior and su[)ero-lateral portions 
of the bone occu[)ying the position of the lambdoidal crest are unfortunately broken 
away, but it can be seen that in conjunction with the neighbouring scpiamosals and 
parietals the body of tlie bone is excavated by a series of large cellnlar cavities, 
