Sinclair: typotheria of the santa cruz beds. 
21 
capitis muscles. About midway, the occipital plate is strongly constricted 
transversely, lodging the mastoid foramen on the suture between the mas- 
toid and the occipital at the point of greatest constriction of the latter. 
Inferiorly, the occipital expands, supporting long fang-like paroccipital pro- 
cesses, the points of which curve forward. Above the foramen magnum 
the occipital surface is convex, sometimes broadly so, sometimes with a 
slight median keel. The condyles are oblique and semi-cylindrical in 
shape. 
The palate (PI. Ill, fig. 3) is concave in all dimensions, but less deeply 
so antero-posteriorly than transversely. The palatine extends as far 
Protypotherium australe, zygomatic arch removed to show the arrangement of the cranial ele- 
ments in the temporal fossa, x p am, auditory meatus ; as, alisphenoid ; c, condyle ; f, frontal ; 
m, mastoid ; o , optic foramen ; os, orbitosphenoid ; ov, foramen ovale and lacerum medium ; p, 
parietal ; pi, palatine ; pt, pterygoid ; s, squamosal. 
forward as the anterior lobe of M-. Opposite the posterior margin of the 
last molar, it is constricted by deep notches, beyond which it expands 
again, terminating in a pair of triangular rugose processes formed in part 
by the palatine and in part by the alisphenoid. Each process is supported 
by a strong, transverse, plate-like buttress of the alisphenoid, the squamosal 
taking no part in its formation, unlike the structure of this region in 
Hegetotherium (cf. text figs. 8 and 13). The pterygoid is a small, thin 
plate, terminating in upwardly curved hamular processes. Between the 
pterygoid and alisphenoid plate is a deep fossa. In all the specimens 
examined the narial border has been injured and it is not possible to 
ascertain whether a posterior narial spine was present or not. Two pos- 
Fig. 8. 
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P 
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