74 



MEMOIFS OF THE QUEENSLAND MUSEUM. 



Eioyzygoma may be defined as a specialised member of the Nototherian 

 group, and. to use Gregory's terms, its large processes were a cspnotelic 

 character rehited to special food-habits. 



Mandibles. — Unfortunately there is no mandible directly associated with 

 the cranium under review. De Vis (1887, p. 1065) de.scribed three examples, 

 one (No. 5489) being illustrated as the type. His diagnostic characters are 

 here reproduced : — • 



"Tusk-like incisors well developed; premolar small, sub-triangular, 

 unilobate ; inlet of dental canal much behind postmolar angle and much above 

 alveolar level ; exterobasal ridges of molars interrupted : talons anterior and 

 posterior well developed : molars gradually enlarged : inner symphysial curve 

 opposite hinder lob of )n\'' 



A full description of the three examples follows in the original paper. 

 In the following year, De Vis (1888) illustrated the upper subtriangular 

 premolar of " Xototherium dunense," previously referred to in this paper as 

 a heautotype. 



Text-fig. 1. — EuRYZYGOMA DUNENSE. Reconstruction of cranium; one-fifth natural size. 

 Dravn by 0. W. Tiegs. 



Taxonomic. — In classifying the Marsupialia of to-day the premolar is 

 recognised as the most important tooth, and that tooth alone is sufficient to 

 establish the identity of many species. The evidence of divergent premolars is 

 thus not to be lightly put on one side. Lydekker (1889) thought that the large 



