406 ON A FOSSIL HUMERUS, 



thigh bone figured in plate xxxiv. of the " Fossil Mammals." 

 Further, as it is but reasonable to infer that the fore limb cf the 

 animal would be characterised by the like massive simplicity we are 

 perfectly ready to concur with the illustrious author of the Fossil 

 Mammals in attributing to Diprotodon the humerus given in plate 

 xxxi., it is in fact, just such a bone as we should have looked for. 

 From that recognition we should obtain a just conception of the 

 general form of the arm-bone of Nototherium, assuming only that 

 it was rather more unlike that of the Wombats than the one 

 delineated. If on comparing Diprotodon and Phascolomys, we are 

 most willing to admit that the very unlike teeth of the Wombat 

 are attended by a very unlike humerus, a bone formed by or for 

 powerful action in different directions, squat, angular, twisted and 

 covered with ridges and asperities, as wont is with fossorial arm- 

 bones we are the less disposed to look in that direction for the 

 humerus of Nototherium. It is therefore with perplexity that we 

 look upon the bone figured in plate xxxvu., as the Nototherian 

 humerus — a perplexity increased by the absence of any reasons 

 declaring for the determination. Nototherium, Owen, as established 

 on the teeth, and Nototherium, Owen, as represented by the 

 humerus, are or appear to be two animals — it would be highly 

 interesting to know why we should believe in their identity. The 

 subject of plate xxxvu., is pronouncedly phascolomine. Prof. 

 Owen directs our special attention to the phascolomyan characters 

 which may in truth be said to be exaggerated in it. If the bone be 

 really the humerus of Nototherium, that animal could scarcely 

 have been a remove from the genus Phascolomys, and it was 

 to all appearance a burrower, whilst its relative the Diprotodon, 

 said to be the nearer to Phascolomys by dentition, was 

 in the structure and office of its fore limb a mere marcher. It 

 is surely improbable that so great a difference should exist between 

 the arm-bones of two animals so closely allied in dental characters 

 as to have been nearly placed at first sight in the same genus 

 without direct or at least good constructive proof to the contrary, 

 we cannot allow a much greater latitude of differentiation to the 

 limb bone than we find in the teeth. On the other hand, we 



