408 ON A FOSSIL HUMERUS, 



i. e., in the middle of the outer edge, but by no means the same 

 form, in Diprotodon, it is a compressed widely expanded ridge, in 

 Nototherium a bilobed tuberosity. The rough surface on the 

 upper part of the back of the shaft described and figured as a well- 

 defined oval in Diprotodon is in Nototherium very rugose, but 

 shapeless and indefinite in extent. The lateral expansion of the 

 distal end of the shaft has a gradual increment in Diprotodon, a 

 comparatively sudden one in Nototherium. The inner condylar 

 ridge is, as might be expected imperforate in the smaller, as it is in 

 the larger animal — otherwise also they are much alike in this 

 region. In the ectocondylar ridge on the other hand, they differ 

 markedly. In Nototherium it commences much nearer the 

 external ridge, and is suddenly flattened out into an almost wing- 

 like expansion ; it is also much less angular. The condyles in 

 Nototherium are relatively less in fore-and-aft thickness, and are 

 set on much more obliquely to the long axis of the bone. In form 

 they differ but little from those of Diprotodon, but the trochlear 

 constriction between them is much greater. The olecranal fossa is 

 more limited in extent and of greater depth. 



It will be seen that the characters of the bone under examination 

 bring it well within the range of family resemblance, and at the 

 same time keep it aloof from a strictly generic likeness to the 

 humerus of Diprotodon. It may be acknowledged that these are 

 conditions which can only be fulfilled by a humerus of Nototherium. 

 Should this judgment appear sound, the theory which has gained 

 popular headway that Nototherium was an animal midway between 

 a Kangaroo and Wombat, will be so far unsupported. Deprived 

 of its phascolomine arm-bone, it will appear that, inasmuch as it 

 was a marsupial and a herbivorous one, it had certain minor points 

 of resemblance to its extant relatives, but that these are in them- 

 selves quite insufficient to prove that its relatives are anything 

 nearer than cousins germane. 



