102 
TEETIAKY VEUTEBEATA OE THE FATOM. 
PalaeomastoRon and the later Proboscidea. The supraoccipital, together with that 
|)ortion of the exoccij)itals above tlie foramen magnum, forms a sort of escutcheon- 
sliapcd area, which ])rojects a little behind the rest of the occipital surface formed by 
the exocci])ital-squamosal plate above referred to. One peculiar feature is, that 
l)etween the lower end of the lambdoidal border of the supraoccipital and the occipital 
|•('gion of the squamosal, a small triangular process of the parietal is interposed, this 
l)one thus assisting in the formation of the occipital surface (PI. VIII. fig. 1 pa., and 
ri. X. fig. 4 A, ])a.). 
'fhe squamosal [sq.) is a very large and massively constructed bone, in which it 
ap])ears that the development of the diploe, carried to such a high pitch in later types, 
has already begun ; and on the upper surface of the bone above the auditory opening 
there are several foramina (PI. VIII. fig. I, /or.) communicating with the interior, just 
as in l^alceomastodon : this inflation of the squamosal is especially well shown in the 
type skull of M. gracile (PI. XVII. fig. 2). The posterior portion of the bone forms 
the outer part of the occipital surface: internally it unites with the exoccipital, but it 
is excluded from contact with the supraoccipital by the process of the parietal above 
referred to. This post-tympanic region of the squamosal forms the posterior wall of 
the external auditory meatus (Pis. VIII., IX. fig. 1, e.a.m.), and closes it ventrally by 
uniting wdth the posterior edge of the glenoid surface, just as in Palceomastodon and 
the later Proboscidea. The lower border of the post-t}'mpanic process {ptg.) extends 
considerably below the glenoid surface and forms a sort of spurious postglenoid 
process ; internally it is wedged between the glenoid surface and the paroccipital 
process of the exoccipital. Superiorly the squamosal unites with the parietal, the 
suture wdth which runs down to about the middle of the temporal fossa, but, owing 
to the condition of that part of the skull, cannot be traced further. The zygomatic 
process is large and projects strongly on the side of the skull. It is triangular in 
section : the upper edge is continued upwards on to the side of the skull, forming the 
lower portion of the lambdoidal ridge ; the outer edge turns inwards and forms the 
])osterior border of the glenoid surface. This surface is very large, extending from 
the outer edge of the zygomatic process inwards almost to the level of the pterygoid 
processes. It is concave from side to side and strongly convex from l)efore backwards, 
])articularly anteriorly. A portion of its antero-external border is formed by the hinder 
end of the jugal. The posterior portion of the glenoid surface is borne uj)on the shelf- 
like projection, of which the upper surface forms the floor of the auditory opening. 
4’he tympanic is so much crushed and obscured by matrix that neither it nor the 
foramina in its neighbourhood can be described. 
The ]>arietals {paf, as already described, send back a short ])rocess on to the 
occipital surface on either side. Above they unite with the su})raocci])ital, which 
sends a process between them for some distance. In front of this they meet one 
another in the middle line and form a not very prominent sagittal crest for some 
