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Show 782 PROF. BALDWIN 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 premaxillae 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 tbe 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 (PL X L I X . 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 tbe 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, Phascolomgs, and Dasgurus, but is quite wranting in other forms such as Phascolarctos and Sarcophilus. The foramen rotundum opens close to tbe 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 tbe 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. Tbe same feature occurs in Macropus, Sarcopdiilus, 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 m m . by 5 m m . 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 |