OF THE AUSTEALIAN MAESUPIALIA. 117 



the typical method of the formation of a quadrate tootli is iUustrated by the teeth of 

 the Condylarthra and Peramelinte, on the one hand, and the atypical method by those 

 of the Amblypoda and Thylacomys. All of these facts indicate that the main cusps 

 represented in the typically qviadrituberculate Phalanyeridte and their herbivorous 

 derivatives are directly homologous with those of the Peramelinse. 



Tlie lower teeth of the advanced quadrituberculate forms call for no consideration, 

 since in the Tliylacomyinse, as also in the Amblypoda, they show no departure from the 

 condition in other forms. 



NOTORYCTID^. 



During the twelve years which liave elapsed since the original description of Notoryctes 

 by Stirling (.1891), the dental characters of the animal have been commented upon by 

 several writers, including Ogilby (1891), Cope (1892), Gadow (1892), Winge (1895), Forsyth 

 Major (1897), Spencer (1896), and Tomes (1899). The following remarks are therefore 

 largely directed towards an arrangement and discussion of opinions already expressed. 



It may be observed at the outset that no adequate conclusions concerning the affinities 

 of Notoryctes can be formed from a study of the dentition alone. While the median 

 lower incisors present an undifferentiated condition, which shows the animal to be related 

 to the members of the polyprotodont section, namely the Dasyuridoe and Peramelida?, the 

 dentition is otherwise so completely modified away from the usual polyprotodont type 

 that it does not present any of those special characters which distinguish the lattei- 

 families from one another. As will be pointed out in detail in a subsequent section, in 

 the absence of definite characters of dental affinity in Notoryctes the primary characters 

 which separate the Dasyuridae from the Peramelidte do not relate to dentition, and in 

 addition do not represent merely a family distinction, but, on the other hand, serve to 

 separate the Dasyuridfc from all of the remaining Australian forms. These characters 

 may be mentioned as relating to the non-syndactylous and syndactylous modificiitions 

 of the second and third digits of the pes, respectively characteristic of the two series. 

 Notoryctes, in its foot-structure, shows affinities with the syndactylous section, indicating 

 that of the two polyprotodont families its relations are rather with the Peramelidte than 

 w'lih. the Dasyuridae. These relations should be borne in mind in attempting to derive 

 the characters of its dentition. 



Dental Formula. — A conspicuous feature of the dentition of Notoryctes, and one which 

 is in all probability responsible for most of the remaining characters presented, relates t.o 

 the foreshortened condition of the tooth-rows. One of the effects of this development 

 is seen in the variability of the dental formula, implying a reduction, w liich is still in 

 progress, of certain of the less functional teeth. The formula has been variously 

 determined by Stirling, Ogilby, Gadow, and Spencer, the most trustworthy figures being 

 those given by the last-named writer. Spencer states that the full formula, " as far as at 

 present known," is : /. ^, c. |, p. ', m. ^. Concerning this he remarks as follows (p. 4.7) : — 

 " It was only alter examining twenty-nine specimens that one was found in which the 



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