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Show 780 PROF. BALDWIN SPENCER ON A [NOV. 20, to the straightness and to a certain extent the length of the squamosal suture, the fossil resembles Phascolomys andPhascolarctos, from both of which it differs, however, to a great extent in other features. The squamosal is indeed larger than in any existing or fossil marsupial yet known, and its forward extension completely prevents the alisphenoid from coming into contact with the parietal as it does in most marsupials, such as Phalanger, Trichosurus, Pseudochirus, and Dasyurus; though, on the other hand, the parietal does not reach the alisphenoid in Peragale, Mpyprymnus, and Phascolomys, with which in other respects the fossil has but little in common. N o intertemporal bone can be detected. The zygomatic arch is strong and massive, most resembling in form that of the Dasyuridae both in the considerable outward sweep of the hinder part and in its marked upward curvature; in the former respect it most nearly resembles a large skull of a Dasyurus, and in the latter that of a Sarcophilus. There is not a trace of the swollen posterior part of the squamosal which is such a striking feature in certain of the Phalangeridae, such as the genera Phalanger, Trichosurus, Pseudochirus, and Petaurus ; but, in strong contrast to what is characteristic of these forms, the arch arises low-down, and, as is well seen in lateral view (fig. 5, PI. L.), the upper surface rises immediately so as to form a strongly marked curve: at the same time the arch flattens out laterally, bends over (fig. 1) towards the upper surface and runs forwards to be inserted into the notch in the malar process of the maxilla. The latter process is w-ell developed and passes off almost at right angles to the side of the maxilla, bending abruptly backwards and at the same time outwards to be attached in the characteristic way to the hinder end of the arch, beneath which it runs backwards to the glenoid cavity. The abrupt bend of tbe malar process most resembles that of Phascolarctos, though in the latter the main body of the arch runs parallel to the length of the skull. In the Phalangeridae the bend is a more gradual one, and the sweep of the arch is not nearly so pronounced as it is in this fossil form. Though the lower part of tbe arch is broken away, it appears probable that there was a slight zygomatic process at the anterior end; and, as iu Trichosurus and certain other genera, only still more markedly, there is a very distinct ridge (PI. L. fig. 5), which traverses almost the length of the arch, and sharply marks off an outer and upper from an outer and lower surface, the latter serving for the attachment of the masseter muscle. The glenoid cavity is considerably elongated transversely, the downward process which bounds it posteriorly being, as in the Dasyuridae and Perameles, apparently independent of any structure concerned with tbe auditory passage. The shape and relationships of this process are most similar to those of Thylacinus, and differ markedly from those which obtain in tbe Phalangeridae, amongst the members of which the process in question forms the anterior part of a well-marked bony canal. Also, as in Dasyurus, the |