ICO DR. B. A, BENSLEY OX THE EVOIXTIOX 



transverse crests {cf. PI. 5. fig. 25 & PI. 6. fig. 31). If one may judge by analogy with 

 the latter family, these teeth are of quadrituberculate hunodont orighi, as are also those 

 of the Phascolomyida?. In both upper and lower teeth the transverse crests are greatly 

 elongated vertically, as in the Macropodina?, but unlike the latter they are also curved. 

 The longitudinal crests characteristic of most of the Macropodinfe are not represented. 

 The upper molars show the anterior basal cingular ridge which is commonly developed 

 in the latter group. The lower molars show a posterior cingular ridge which is not 

 represented in the Macropodinfe. 



The molar characters of the smaller form, Nototheriam, are much as in Biprotodon. 

 There is a trace of a longitudinal band in the median valley. In this character 

 Nototherlum is slightly more primitive, because, while longitudinal bands are highly 

 characteristic of the more specialized of the Macropodidae, their actual presence is a 

 primitive phalangerine character, and their absence is secondary. 



Incisors — The incisors of Biprotodon are in genei'al intermediate in character between 

 those of the Phalangeridte and those of the Phascolomyidai. The median upper teeth 

 are open-rooted, arched, and scalpriform, as in tlie latter family. They are even more 

 specialized as regards the differentiation of the enamel bands. The second and third are 

 retained, and serve as stops for the lower teeth, as in the Phalangerida3 ; but, unlike 

 the latter, they are also open-rooted. 



Nototherium approaches Biprotodon in that the second and third upper teeth are 

 present and those of opposite sides are in contact in the middle line. The median upper 

 and lower teeth are of a more primitive type, neither being scalpriform. The lower 

 especially are rounded in section and definitely pointed. It is interesting to note that 

 among the fossil forms referred to the Macropodidae we find two types of lower incisors, 

 the latter being usually of a spatulate cutting type, as in the existing forms of grazing 

 Macropodinge, but sometimes {Trocoptodon) of a pointed piercing type, as in Nuto- 

 theriuni. Considered alone, the lower incisors of Trocoptodon would be readily taken as 

 belonging to a lower and smaller member of the Kototherium- Biprotodon line. 



Premolars. — As in the Phascolomyidse, only the posterior teeth are represented. 

 The following comparisons include only the lower ones. In 'Nototherium these teeth are 

 very much as in Fhascolomys, except that they are not open-rooted. They are com- 

 paratively poorly develojjed ; they show a main anterior cusp, and a posterior crest 

 formed by the connection of two cusps. In Biprotodon, also, these teeth are poorly 

 developed. When slightly worn they present anterior and posterior crests, the former 

 appearing imperfect. The posterior crest obviously corresponds to that in Nototherium, 

 although better developed than in that form. The anterior crest cannot be regarded as 

 having arisen from the connection of two opposite cusps, as in the molars, because no 

 case occurs in the herbivorous Marsupials where these arc found in posterior premolars, 

 the only conclusion being, therefore, that it is the result of compression of the anterior 

 cusp found in the smaller forms, Nototherium and Fhascolomys. 



It will be seen that, although the dental characters of both families are highly modified 



