782 PROF. UALDAVIN SPENCER ON A [NOV. 20, 



to those of Trichosurus, and their dimension would appear to 

 indicate the existence of a fair-sized incisor dentition. It is most 

 unfortunate that the lower part of the premaxillse should have 

 been broken away at such a level as to leave no indication of the 

 exact nature of the teeth. 



With regard to the ventral surface, the specimen is so broken 

 that it is not possible to say much. The palate is completely 

 wanting ; parts of the basi- and presphenoid remain and the 

 euto-carotid canals, as is characteristic of marsupials, pierce the 

 basisphenoid and enter the skull close to the middle line, the 

 opening on the right side being larger than that on the left. 

 Each artery runs forward in a deep strongly marked groove, the 

 two grooves converging anteriorly. These grooves, which lead 

 forwards from behind the level of the foramen ovale on each side, 

 are considerably longer and more strongly developed than in any 

 other marsupial and are well seen in the figure of the under surface 

 of the skull (PI. XLIX. fig. 2). 



The foramina leading from the skull, so far as they remain, 

 agree in essential features with those of marsupials. The optic 

 foramen and the foramen lacerum anterius are united to form a 

 sphenoidal foramen opening outwards from the sella turcica, and 

 the foramina of the two sides are confluent, so that in lateral view 

 (fig. 5) of the skull there is a small but well-marked opening 

 leading from the lower part of the temporal fossa of one side into 

 that of the other. The passage thus formed is bounded below 

 by the basisphenoid and presphenoid, the suture between which 

 lies in the floor of the cavity, and above by the ali- and presphenoids. 

 A similar passage is seen in Macropus, Trichosurus, Pseudochirus, 

 Phascolomys, and Dasyurus, but is quite wanting in other forms 

 such as Phascolarctos and Sarcophilus. The foramen rotundum 

 opens close to the outer and slightly to the under and posterior 

 side of the sphenoidal foramen, from which it is as usual only 

 separated by a thin plate of bone. 



Within the cavity of the skull the entocarotid canals enter close 

 behind the sella turcica, the right being twice the size of the left. 

 The sella turcica has no posterior clinoid process, and from the 

 foramen rotundum of each side a well-marked groove leads back 

 to the Gasserian fossa, the outer edge of the groove being formed 

 by the projecting ridge of bone which is developed from the 

 alisphenoid in the tentorial plane. The same feature occurs in 

 Macropus, Sarcophilus, and Dasyurus. The periotic lies completely 

 behind the ridge marking the tentorial plane, the bony structure 

 in which is not very strongly developed in contrast with what 

 obtains, for example, in Cuscus and Trichosurus. The periotic 

 differs from that of other marsupials, first in its relatively small 

 size, and secondly in its structure. The lower part, in which lies 

 the auditory meatus, has, facing the cerebellar cavity, a nearly 

 vertical surface measuring 8 mm. by 5 mm. in height ; above this 

 portion the bone is impressed so as to form a horizontal platform 

 from which, on the outer and posterior sides, rise the thin curved 



