SINCLAIR: MARSUPIALIA OF THE SANTA CRUZ BEDS. 379 



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 Thylacymis 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 Protkylacynus. 



The basioccipital and basisphenoid (PI. LV, fig. i) are flat, unlike 

 Frothy lacynus, 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. i ; LXI, fig. i). The anterior coronoid border is straight 



