364 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



In the posterior view (PI. XLVIII, fig. 3), the occiput is seen to be 

 quadrangular in outline, unlike the triangular occiput of Thylacynns. Its 

 upper border projects considerably beyond the condyles. The exposure 

 of the mastoid is relatively smaller than in Thylacynns. 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. PL LXV, fig. 10). 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 Thylacymis. 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 Thylacynns, 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 TJiylacynus. 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 Thylacynns, 

 is but slightly developed and is entirely wanting posteriorly. The post- 

 glenoid processes are proportionately shorter than in Thylacynns, 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 Thylacynns. 

 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 Thylacynns 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 Thylacynns symphysial 



