274 LLOYD’S NATURAL HiSTORY. 
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. 
A, a Ae 
oo 
Je 
a 
ya (Ave/ 
~ < E 
Diagram of Molar Teeth of Secondary Marsupials, seen from the outer 
side, and superposed in mutual relation. 2 Dromatherium, 3 Triconoaon, 
4 Spalacotherium. (From Osborn.) 
GENUS TRICONODON. 
Triconodon, Owen, Encyclopedia Britannica, 8th ed., vol. xvii., | 
p. 161 (1859); Lydekker, Cat. Foss. Marsup. Brit. Mus., 
pt..¥., p. -259 (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 (Z. major) may be compared in size to the 
existing Dasyurus viverrinus. Allied forms from the Upper 
Jurassic rocks of the United States have been assigned to a | 
distinct genus, although they do not really appear separate from | 
the present one, : 
