364 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
In the posterior view (PL XLVIII, fig. 3), the occiput is seen to be 
quadrangular in outline, unlike the triangular occiput of Thylacynus. Its 
upper border projects considerably beyond the condyles. The exposure 
of the mastoid is relatively smaller than in Thylacynus . Unlike that genus, 
the condyles are wider dorsally, more obliquely placed and less sessile. 
The base of the skull is in excellent preservation, permitting full com- 
parison with the recent genus (cf. PI. LXV, fig. 1 a). The basioccipital is 
broadly keeled below. The paroccipital processes are short, blunt and 
massive. The condylar foramen is large. It is preceded by a very small 
accessory foramen. The tubercles for the origin of the recti capitis muscles 
are about as large as in Thylacynus. The alisphenoid is without dilata- 
tion and does not form an auditory bulla. It is perforated by the foramen 
ovale directly opposite the glenoid cavity. The tympanic is unfused with 
the elements adjacent and has not been preserved. The petrous is larger 
and more completely hemispherical than in Thylacynus , the relative po- 
sition of the fenestrae remaining the same. 
The basisphenoid is broadly keeled and convex in cross section in con- 
trast with its plane, or slightly concave section in Thylacynus. It is per- 
forated by a single canal, that for the internal carotid artery. The ali- 
sphenoid ridge, which is confluent with the auditory bulla in Thylacynus , 
is but slightly developed and is entirely wanting posteriorly. The post- 
glenoid processes are proportionately shorter than in Thylacynus , but the 
preglenoid processes are much larger. The foramina of the lateral 
sinuses, especially the post-glenoid and sub-squamosal, are larger than in 
the recent genus. A small foramen pierces the jugal process of the squa- 
mosal above the glenoid cavity, as in some specimens of Thylacynus. 
The palate is without vacuities, but is pierced by several accessory palatal 
foramina. Its posterior margin is perforated by a double neuro-vascular 
canal. The narial border is slightly thickened. The margins of the 
palate are depressed to accommodate the tips of the lower molars, as in 
most carnivorous marsupials. 
In proportion to its length, the mandible is much deeper than in Thy- 
lacynus. The anterior margin of the coronoid is convex, in contrast with 
its slight concavity in Thylacynus and is less steeply inclined posteriorly ; 
the masseteric fossa is more broadly rounded anteriorly and the posterior 
margin of the angle less deeply notched. Both rami are firmly coossified 
in the symphysis without trace of suture, while in Thylacymis symphysial 
