Implement and Bones of Extinct Kangaroo. 83 



the same side appears a marked hollow (b), at the bottom of 

 which the cancellous structure of the interior of the shaft has 

 been by the like means brought into view. 



So far the abnormal features observable are not of intrinsic 

 importance. They may have been the result of ordinary physical 

 agencies of attrition. A similar explanation of the condition of 

 the lower end of the bone, or at least of one edge of it, is, on the 

 contrary, inadmissible. On its posterior face (Fig. 2) the rib has 

 here been half sundered by a cut tlirough its dense cortex (r), 

 effected by strokes of a sharp instrument. A little lower down 

 on its opposite face (Figs. 1 and '2d), it has been divided to 

 a like extent, and the part beyond the two nicks so made has 

 broken off", the line of fracture naturally occurring between 

 them. The extreme edge of the fracture was thus brought to 

 coincide with the inner edge of the lower nick, and this conse- 

 quently presents a fairly sharp edge, rendered somewhat jagged 

 by adherent remains of the internal cancelli. The surface of the 

 lower nick (Fig. \d) is convex in both its directions of extent, 

 but whether this rounding oft' is the result of an original method 

 of formation by filing, scraping, or shearing tool, or by the subse- 

 quent grinding of a surface in whatever way produced, is not to 

 be gathered from the existing surface. In the latter case it is of 

 course quite possible that this bevelled surface also might have 

 been the outcome of mere physical action on a piece of rib lying 

 in a watercourse or sand-drift, with one end partially exposed ; 

 it is even possible that the severance of the bone on this side of 

 it was due to such cau.se. But these conjectures seem to be 

 entirely forbidden by the complete absence of any sign of abra- 

 sion on the inner side of the edge of the nick ; the broken walls 

 of the bone cells, even at its extreme edge, are as sharp and 

 prominent as they were left by their fracture, and we are there- 

 fore driven to the conclusion that this surface, however formed, 

 was intentionally formed. That the surface of the upper nick — 

 that on the opposite side of the bone (Fig. 2c) — could not have 

 been yielded by any physical process, is on the other hand 

 unquestionable. It is certainly the work of an animal possessed 

 of a chopping instrument, and as far as we know the only 

 animal of the age of the Nototherium that can excite even a 

 passing suspicion is the so-called Marsupial Lion, Thylacoleo 



6a 



