SINCLAIR: MARSUPIALIA OF THE SANTA CRUZ BEDS. 2>19 
feeble temporal ridges converge to form a long, high sagittal crest, the 
top of which is practically horizontal. In C. petersoni , only a small por- 
tion of the anterior extremity of the crest is preserved, but this rises 
abruptly above the interorbital tract, with decidedly convex superior 
border. The crest terminates posteriorly in a semicircular lambdoidal 
frill, which does not project beyond the condyles. The supraoccipital is 
broadly expanded on the upper surface of the brain case. Between the 
supraoccipital and the squamosal, a narrow tongue of the parietal reaches 
the mastoid border of the occiput. The orbits are proportionally smaller 
than in Thylacynus and are placed much farther forward, their anterior 
border coinciding with a line drawn through the posterior half of the first 
molar. A large lachrymal prominence is situated on the orbital rim 
above the lachrymal duct, which lies wholly within the orbit. 
The occiput is semi-circular in outline, so far as can be judged from 
the crushed specimen (No. 15,170), in which this portion of the skull is 
preserved. The mastoid is exposed to about the same extent proportion- 
ately as in Prothylacynus . 
The basioccipital and basisphenoid (PI. LV, fig. 1) are flat, unlike 
Prothylacynus , resembling in this respect the recent genus. The paroc- 
cipital processes are broad, dome-shaped masses, lying considerably below 
the level of the auditory bullae. The latter are formed entirely from the 
dilated alisphenoids, the petrous not entering into the posterior wall of 
the bulla, as in some of the dasyures. A large foramen ovale pierces the 
alisphenoid opposite the glenoid cavity. The palate begins to increase 
in width back of the posterior premolar and is without vacuities, but is 
pierced by several accessory palatal foramina. The anterior palatine 
foramina project a short distance beyond the premaxillo-maxillary suture. 
A pair of large foramina pierce the maxillary on either side of the median 
line, either opposite or a short distance anterior to the posterior border of 
the canine. The usual thickening is observable about the border of the 
posterior nares. The foramina opening into the lateral venous sinus are 
large, sub-squamosal, post-glenoid and post-zygomatic foramina being 
present. The last mentioned opens well within the lip of the post-glenoid 
foramen. A small foramen pierces the outer side of the squamosal bar 
above the glenoid cavity. 
In contrast with the skull, the mandible is remarkably deep and heavy 
(Pis. LVI, fig. 1 ; LXI, fig. 1). The anterior coronoid border is straight 
