SINCLAIR: TYPOTHERIA OF THE SANTA CRUZ BEDS. 
73 
broadly exposed. The occipital elements are fused to such an extent that 
it is impossible to differentiate between supra- and exoccipitals. Dorsally, 
the occipital is broad, a wing-like expansion overlapping the mastoid dila- 
tation. About midway between the lambdoidal crest and the foramen 
magnum the width of the occipital decreases sharply. This constriction 
lodges the mastoid foramen, which perforates the occipito-mastoid suture. 
When not obliterated by fusion, the mastoideo-posttympanic suture trends 
outward and downward from this point (text fig. 14) for about two-thirds 
of its course, thence rising toward the border of the occiput at a point 
opposite the lower margin of the auditory meatus. Opposite the con- 
dyles the occipital attains its maximum expansion, but does no reach 
the border of the occiput, where the post-tympanic area is exposed. In- 
teriorly, the exoccipital portion is greatly elongated, forming the fang- 
shaped paroccipital process. The occiput is divided by a slight ridge 
extending from the lambdoidal crest to the foramen magnum. The latter 
is elliptical in outline, with the condyles obliquely placed. The condylar 
surfaces are divided into posterior and inferior moieties by a low but per- 
fectly distinct ridge, coinciding with the inferior border of the condylar 
surface as seen in posterior view (PI. I, figs. 3, 4). These surfaces are 
convex in all dimensions, but are comparatively flat when contrasted with 
the semi-cylindrical condyles of Protypothevium. 
The palate (PI. I, fig. 3) is moderately concave. The tooth-rows are 
straight posteriorly, converging rather sharply anterior to the second pre- 
molar and again becoming straight or nearly so. The palatine extends 
as far forward as the middle of the first molar. Opposite the middle of 
the second molar the maxillo-palatine suture is perforated by the posterior 
palatine foramina. The narial border is emarginated by a strong spine. 
Posteriorly, the palate resembles that of Protypothevium , terminating in a 
pair of processes with knob-like extremities, which are partly developed 
from the palatines and partly from the alisphenoids. Each process is sup- 
ported externally by a plate-like buttress (text fig. 16, as) developed 
from the alisphenoid and squamosal, directed outward and backward and 
coinciding with the line of suture between the alisphenoid and the squa- 
mosal, while in Protypothevium it is directed mainly outward. The ptery- 
goid is not preserved in any of the skulls examined, but, with the 
alisphenoid plate, incloses a deep fossa as in Protypothermm. The squa- 
mosal is peculiar in that it sends a long process upward and forward to 
