242 REMARKS ON POST-TERTIARY PHASCOLOMYID.E, 



the shaft at the base of the outer condyle of platijrhinus there is 

 no trace in the fossil. 



Two forms of tibia present themselves, one (with three examples) 

 much less unlike that of P. platyrhinus than the other, but, never- 

 theless, to be preferred for reference to P. mitchelli, for though 

 unexpectedly thin and angular it is much less so than its companion. 

 With extremities no greater in size, the fossil of this form is in its 

 total length distinctly (one-twelfth) greater than in recent bones. 

 Compared with the humerus it must, therefore, be considered 

 slender. In general shape it is like that of platyrldnus, but its 

 shaft has a little stronger curve and a rather greater dilatation of 

 its edge at the junction of the proximal and middle third of its 

 length. The posterior surface of the shaft is broader and flatter 

 and its edges, but especially the distal half of the inner edge, are 

 sharply angular. The cavity for the outer condyle of the femur 

 is, unlike that of platyrhinus, circular; the space between it and 

 the procnemial tuberosity much more elevated, causing the articu- 

 lating part of the head, when viewed laterally, to appear much 

 longer ; the tuberosity is shorter, the inner edge of the entocondylar 

 surface is not produced into a point adjacent to the facet for the 

 head of the fibula, and the spine is both higher and sharper. At 

 the distal end the anterior edge of the shaft is more compressed, 

 the scaphoid moiety of the inner malleolus is narrower and more 

 sharply grooved off from the rest of the malleolus. Perhaps no 

 one of the several differences which have been noticed would be 

 sufficient of itself to distinguish this tibia from others, but, taken 

 together, the discrepancies between it and that of •platyrhinus are 

 altogether prohibitory of specific identity between the two. Of 

 this bone the collection contains one nearly perfect from the right 

 side and two opposite halves from the left side. 



Until it can be shown that the fossils which have been brought 

 forward are not really bones of P. mitchelli, that is until genuine 

 bones of P. platyrhinus are found fossil on the Con dam in e, or 

 until another species of extinct wombat to which they can more 

 probably be referred becomes known, it may, I think, be accepted 



