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Show 1900.] FOSSIL MARSUPIAL FROM TASMANIA. 787 mitchelli 85*4. It will be observed that there is a very considerable variation within the limits of the Phalangeridae, the fossil having a decidedly shorter femur than is found in Trichosurus and a decidedly longer one than in Phalanger, while it agrees very closely with that of Sarcophilus. The Tibia (fig. 9, PL L.).-The tibia is a strong bone with the shaft much compressed and twisted. At about a fifth of its length from the upper end there is a well-marked tuberosity, flattened from side to side and considerably more prominent than in the tibia of Phalangeridae or Dasgurus, though not so strongly marked as in Phascolarctos, where it forms a very prominent structure with an extended broad surface. The inner articular surface of the head is of much greater extent than the outer, in correspondence with the large size of the inner condyle of the femur. In this feature it differs from the tibia of recent marsupials. Wynyardia bassiana. Portion of right fibula, anterior aspect. The same, posterior aspect. Both nat. size. The Fibula (text-figs. 3 & 4).-Tbe fibula is a complete separate bone. Unfortunately neither fibula is perfect distally, but sufficient of this end of tbe right one remains to indicate that though the head was somewhat expanded, it was considerably less in size than that of the tibia. Tbe proximal end is much enlarged, the most noticeable features being (1) the fact that evidently the outer condyle of the femur, as in 1 hascolomys and to a certain extent Phascolarctos, articulated with the upper of the two articular facets, the outer head of the tibia playing upon the lower one; (2) the extension upwards of the olecranon portion (broken off in the specimen fio-ured), which carries a well-marked surface with which, as in other marsupials, a sesamoid evidently articulated. The lower tuberosity is strongly marked and in general features the head of the fibula rather calls to mind that of Phascolomys and to a lesser degree that of Phascolarctos. In both of these a line drawn through the middle of the lower tuberosity at right angles to the Ion g axis of the bone lies considerably below the level of the lowest an°le of the tuberosity which articulates with tbe sesamoid, while P R O C . Z O O L . S o c - 1 9 0 0 , N o . LII. 52 |