OF THE AUSTEALIAN MARSUPIALIA. 



19- 



but tlio dental evolution changes from omnivorous to lier])ivorous, and only culminates 

 in. terrestrial derivatives of that family. The latter include the Macropodidse, Diproto- 

 dontidie, and Phascolomyidie. The present family and tlie Notoryctidse are early 

 terrestrial derivatives of the same general line, in Avhich the dental evolution has 

 been arrested at the omnivorous or insectivorous stage, thence proceeding in special 

 directions. 



The relations of the Peramelidoe are shown by the following characters : — (a) the 

 retention of the polyprotodont modification of the antemoiar teeth ; (b) the development 

 of omnivorous moditications of the molars ; {c) tlie development of terrestrial, and more 

 or less digitigrade, modifications of the pes, the latter being otherwise of an arboreal 



Tliijlacomijs. Chdfropus. 



P. ohesuJu. 



P. moresbyeiisis. 



P. Cockerelli. 



P. Doreyana. 



macrura. 



P. Raffrayana. 



Propcramelidag 

 (Arb. prototypes). 



phalangerine type. The first two characters indicate a general ancestral relation of the 

 Peramelidae to the remaining members of the main line, m ith the jiartial exception of 

 the Notoryctidoe, while the third is a primary character of divergence. The presumed 

 common ancestors of the Peramelida? and Phalangeridie are designated in the general 

 plan (p. 192) as Properamelidie (hyp.). 



The present family is notable for the paucity of characters of generic rank. Its 

 special evolution largely concerns the distrilmtion of the species of Feramelcs. The 

 two forms Thijlacomys and Choerojms are independent derivatives of a foi'm not far 

 removed from Perameles Bongainvillei. 



No member of the family combines the characters of a stem-form. P. Doreyana and 

 P. 'Raffrayana are prototypal in their molar patterns, which are only slightly specialized 

 in an omnivorous direction from the insectivorous type presentc;! by the Didelphyidty 

 and smaller Dasyurina?. P. Cockerelli and P. Doreyana are prototypal in the propoitioii 



SECOND SERIES. — ZOOLOGY, VOL. IX. 27 



