396 PATAGONIAN EXPEDITIONS: PALAEONTOLOGY. 



Skull (Pis. LIX, figs. i-3; LX, figs, i-ic, 3). The facial portion of 

 the skull is short and slender, the cranial portion elongate, with low sagittal 

 and lambdoidal crests, widely expanded arches and exceptionally long, 

 shallow brain-case. In profile (PI. LX, fig. i), the upper margin is 

 almost horizontal, becoming slightly convex back of the orbits. The 

 ascending premaxillary processes are short, proportionately less elongated 

 than in Thylacynus and Dasytirus. The nasals are greatly expanded 

 posteriorly and in broad contact with the lachrymals. The lachrymals 

 are large, spreading out on the face and excluding the maxillae from the 

 anterior border of the orbit. The lachrymal duct opens within the orbital 

 rim, which is sharply defined, with a distinct lachrymal tubercle. The 

 infraorbital canal is single, opening externally above the posterior pre- 

 molar. The orbits are large and placed well forward, their anterior 

 border lying above the middle of M 1 . The postorbital processes on the 

 frontal and jugal are small. The zygomatic arches are robust and broadly 

 expanded, the greatest width occurring at about the middle of the arch. 

 The jugal bar bears a well-marked ridge, situated about a third of the dis- 

 tance from its inferior border, for the origin of the anterior portion of the 

 masseter. Posteriorly the jugal is continued to the glenoid cavity, of 

 which it forms the anterior border. 



The postorbital constriction of the brain case is even more marked than 

 in the opossum. A short distance anterior to the point of greatest con- 

 striction the feeble temporal ridges unite to form a low sagittal crest. 

 The supraoccipital, unlike its condition in Prothylacynus and Borhycena, 

 has considerable anterior expansion on the upper surface of the skull, 

 rather more proportionately than in Dasyunis niactilatus and the opossum. 

 A broad bar of the parietal extends posteriorly between the supraoccipital 

 and the squamosal to contact with the mastoid. 



The posterior view of the skull (PI. LX, fig. \c] shows the occiput to 

 be almost semicircular in outline, in contrast with the triangular occiput 

 of the dasyures, Sarcophihts and Thylacynus. It does not project beyond 

 the condyles, which are of the same general shape as in Dasynrns. The 

 foramen magnum is elliptical in outline. Its upper border is notched by 

 an irregular vacuity, resembling a similar structure in some of the Macro- 

 podidae. Owing to the scarcity of material for comparison, it can not be 

 determined whether this peculiar feature is normal to the genus. 



The basioccipital is broad and flat. But one condyloid foramen is 



