﻿2 74 ALLEN'S naturalist's LIBRARY. 



four of premolars, and either three or four molars. As in 

 existing Marsupials, but a single pair of teeth in each jaw was 

 replaced by a vertical successor, and the angle of the lower jaw 

 was inflected. The canine teeth were emplanted by two dis- 

 tinct roots ; — a character to which there is an approximation 

 in some of the Bandicoots, where the single root of these 

 teeth is partially divided by a deep vertical groove. 



I 



Diagram of Molar Teeth of Secondary Marsupials, seen from the outer 



side, and superposed in mutual relation. 2 Dromathtrium, 3 Triconoaon, 



4 Spalacotherium. (From Osborn.) 



GENUS TRICONODON. 



Triconodon, Owen, Encyclopaedia Britannica, 8th ed., vol. xvii., 

 p. 161 (1859) ; Lydekker, Cat. Foss. Marsup. Brit. Mus., 

 pt. v., p. 258 (1887). 



This, the single well-established genus of the family, is re- 

 presented by three species from the Purbeck beds of Dorset- 

 shire, belonging to the upper portion of the Jurassic system, of 

 which the largest {T. 7naJor) may be compared in size to the 

 existing Dasyurus viverri?ius. Allied forms from the UpiDcr 

 Jurassic rocks of the United States have been assigned to a 

 distinct genus, although they do not really appear separate from 

 the present one. 



