172 



DR. B. A. BENSLET OX THE EVOLUTION 



in Notorydes all the digits are much less distinctly separated from one another. The 

 same condition is observable in Phascolomys, also a terrestrial plantigrade type. As 

 shown below, there is not the slightest dovibt as to the derivation of the latter from a 

 normal syndactylons type such as is represented by the arboreal Phalangeridse. As 

 regards the size of the second and third digits in the skeleton of Notoryctes, they are not 

 distinctly more slender than the others, especially the fourth, as in phalangerine forms. 

 The same condition is again observable in some specimens of Phascolomys, although in 

 others they are of the slender phalangerine type. Notwithstanding their uniformity in 

 size, however, the relations between second and third digits in Notoryctes are plainly 

 wath one another rather than with those on either side of them. They show a very 



Eis. 6. 



Dorsal views of phalangerine pes and terrestrial plantigrade modifications. 



A. Trichosurus (after Flower) ; B. Notoryctes (after Stirling) ; C. Notoryctes (B.il. specimen) ; D. Phascolomys (after 

 Owen) ; E. Diprotodon (from Dollo, after Stirling and Zietz). Abbreviations : a., astragalus ; c, calcaneum ; 

 «., navicular : en., entocuneiform ; m., mesoouneiform ; ec, ectocuneiform ; cb., cuboid. 



close correspondence in the general size and length of the metatarsals and phalanges, 

 which is strongly suggestive of former syndactylism. 



Dollo points out a predominance of the fourth digit as a further indication of affinity 

 with the syndactylons series. In Stirling's figure (text-fi.g. 6, B), here reproduced, the 

 fourth digit is seen to project a considerable distance beyond the third. In the spirit- 

 specimen above referred to (PI. 7. fig. 19) the fourth digit does project, in a sense, but 



