]\KEKIT1IERIU.M. 
101 
third molar, but in older skulls in Avhich this tooth has come into wear the openinj^ 
is opposite its hinder end. The palate is narrow and the cheek-teeth are arranged in 
straight and parallel series. 
The hasioGcipital (PI. VIll. fig. 1 a , ho.) is broad and regularly convex from side to 
side, at least posteriorly. Anterioily the crushing that has been undergone obscures 
both tlie form of the bone and its relations to the hasisphenoid, nor are these points 
better seen in other specimens. Posteriorly it is deeply notched by the ventral border 
of the foramen magnum, and laterally it forms the lower ends of the occipital 
condyles. External to the basioccipital is a large foramen, in part no doubt the 
foramen lacerum posterius (f.l.p.) ; the postero-internal angle of this opening forms 
a notch at the point of union of the basioccipital and exoccipital bones, probably 
representing the condylar foramen. 
The exoccipitals {exo.) are very large, and the condyles are strongly convex from 
above downwards, but less so fnun side to side. Above the condyles and over the 
foramen magnum the bones rise nearly vertically, meeting in the middle line in a 
suture about 3 cm. long, thus excluding the supraoccipital from the foramen. Laterally 
and ventrally the exoccipital forms the inner and lower portion of a great flange of 
bone, of which the outer part is formed by the squamosal. This plate of bone adds 
greatly to the width and depth of the occipital surface of the skull, and its ventral 
angle is the equivalent of the paroccipital process of the exoccipital [p-p.). In the 
later type, Falaiomastodon (PI. XII. fig. I), the exoccipital region is drawn out in such 
a w^ay that the condyles project to a much greater degree behind the occipital surface, 
Avhich slopes forwards instead of being nearly vertical. At the same time the flange 
of bone just described is, as it were, pulled out to form the surface lying between 
the hinder border of the glenoid cavity and the occipital condyles, w^hicli surface is 
likewise constituted by the squamosal and the paroccipital portion of the exoccipital 
(see PI. XII. fig. p.p.). In fact, the difierences betw'een this region of the skull in 
Moeritherium and Palceomastodon are just such as would be produced, if the skull of 
the former consisted of a plastic material and the condyles were pulled backwvards so 
as to lengthen the interval between them and the glenoid surface. As will be pointed 
out in the description of the skull of Palceomastodon, the paroccipital process is there 
represented by a blunt tuberosity only. 
The supraoccipital {soc.) is a large somewhat shield-shaped bone. Its upper 
border, forming the upper portion of the lambdoidal crest, is nearly semicircular in 
outline. At its summit the bone is greatly thickened (PI. VIII. fig. 1), and sends 
forwards a triangular process between the hinder ends of the parietals, but there does 
not appear to be any separate interparietal. The occipital surface is raised in the 
middle line into a vertical ridge, on either side of w'hich there is first a slight concavity 
and then a convexity : this median ridge with its accompanying lateral depressions is 
the predecessor of the great depression and ridge for muscle-attachment found in 
