No. 412. THE AUSTRALIAN MARSUPIALIA. 2 
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no doubt as to its composition. Thus the Phalangeridz present 
a typical arboreal modification of the foot, combined with 
advanced omnivorous and herbivorous modifications of the 
teeth, while the Peramelide present a terrestrial modification 
of the phalangerine foot, combined with a primitive omniv- 
orous condition of the teeth. There must, therefore, have 
existed at some time, if the present plan is reliable, a series of 
forms such as is represented in the general diagram on p. 256 
as Properamelidze (hyp.), consisting of animals which combined 
a phalangerine type of foot with a primitive omnivorous denti- 
tion. These animals would have given rise to the Peramelidæ 
by a terrestrial modification of the foot, and to the Phalanger- 
idee by a more completely omnivorous and finally herbivorous 
modification of the teeth. 
From the phalangerine stem, after the omnivorous modifica- 
tion was established, there was apparently given off a branch 
to the Macropodide, with a trend of evolution from arboreal 
to terrestrial, and from omnivorous to herbivorous. The her- 
bivorous modification reaches its greatest development in this 
family. 
The phylogenetic positions of the Phascolomyidae and Noto- 
ryctidae, as indicated in the general plan, are by no means 
certain. In the case of the former, the difficulty in interpret- 
ing the foot structure has already been commented upon. 
The unworn molar teeth of these animals are said by Krefft (75) 
to be quadrituberculate. If such is the case, it would appear 
probable that they arose from the omnivorous arboreal stem 
after the Peramelidze were given off, and that there has been 
a secondary enlargement of the second and third digits. 
In the case of the Notoryctide the writer has not been able 
as yet to decide definitely the cusp homologies in the upper 
teeth, but the lower are undoubtedly tritubercular; as indi- 
cated above, the dentition is probably degenerate. Combining 
this interpretation with the evidence of arboreal characters in 
the foot, it would seem probable that Notoryctes arose from the 
arboreal omnivorous line somewhere near the Properamelidz. 
