SINCLAIR : MARSUPIALIA OF THE SANTA CRUZ BEDS. 397 
present, in contrast with the double condyloid foramen so common among 
existing marsupials. The tympanic (PI. LIX, fig. 2) is annular and 
unfused with the adjacent bones of the skull. The alisphenoid is dilated 
to form the auditory bulla. As this region is imperfectly preserved in all 
the specimens examined, it can not be satisfactorily determined whether 
the petrous was involved in the formation of the posterior portion of the 
bulla, as it is in Dasyurus and Microbiotherium. The basisphenoid is 
ridged, as in existing carnivorous marsupials. Prominent alisphenoid 
ridges extend posteriorly to the confluence with the auditory bullae. The 
pterygoids are not preserved in any of the specimens examined and 
were probably small and scale-like. The posterior nares terminate either 
opposite or slightly posterior to the last molar. The palato-narial border 
is thickened, resembling the corresponding region in the skull of Dasyurus , 
and is more or less emarginate, varying slightly in the degree of develop- 
ment of the median process in different individuals of the same species. 
The palate is long and triangular in shape, increasing in width pos- 
teriorly. Palatal vacuities are conspicuously absent. The incisive fora- 
mina terminate a short distance posterior to the premaxillary suture. A 
large foramen perforates the palatal surface of the maxillary opposite either 
canine. Accessory palatal foramina are less numerous than in Borhyczna. 
The margins of the palate are depressed for reception of the tips of the 
lower molars, when the mouth is closed. The posterior border of the 
palate is perforated by a large foramen on either side of the nares, as 
in nearly all marsupials. 
With a few important exceptions, the cranial foramina are the same in 
number and position as in existing carnivorous marsupials. As already 
noted, the condyloid foramen is single. The basisphenoid has but one 
perforation, that for the internal carotid artery. The foramina of the lateral 
sinuses are especially well developed. The postglenoid and sub-squa- 
mosal foramina are the largest. The postzygomatic, which opens ante- 
riorly within the lip of the postglenoid foramen, varies in size in different 
individuals of the same species. A small foramen occasionally pierces 
the jugal process of the squamosal just above the glenoid cavity. 
The mandible is slender, with moderately convex inferior border. The 
coronoid is less strongly inclined posteriorly than in Thylacynus , resem- 
bling rather the condition in Dasyurus. The masseteric fossa is broad, 
with prominent borders. The condyles have about the same degree of 
