1900.] 



FOSSIL MARSUPIAL FROM TASMANIA. 



7S7 



miicheUi 85 - 4. It will be observed that there is a very considerable 

 variation within the limits of the Phalange ridae, the fossil having 

 a decidedly shorter femur than is found in Trichosurus and a 

 decidedly longer one than in Phalanyer, while it agrees very 

 closely with that of Sarcophilus. 



The Tibia (fig. 0, PI. L.). — The tibia is a strong bone with the 

 shaft much compressed and twisted. At about a filth 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 

 Phalangeridse or Dasyurm, 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. 



Pig. 3. 



Wynyardia bassiana. Portion of right fibula, anterior aspect. 



Pig. 4. 



The same, posterior aspect. Both nat. size. 



The Fibula (text-figs. 3 & 4).— The fibula is a complete separate 

 bone. Unfortunately neither fibula is perfect distally, but sufficient 

 of this end of the right one remains to indicate that though the head 

 was somewhat expanded, it was considerably less in size than that 

 of the tibia. The proximal end is much enlarged, the most notice- 

 able 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 

 figured), which carries a well-marked surface with which, as iu 

 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 

 long axis of the bone lies considerably below the level of the lowest 

 angle of the tuberosity which articulates with the sesamoid, while 



Peoc. Zool. Soc— 1900, No. LTI. 52 



