J 
4 
DROMATHERIUM. PF fe 
of Dorsetshire, which is selected from among several allied 
genera on account of the number of lower teeth being fully 
known. In this genus there were four pairs of incisor, one of 
canine, four of premolar, and either seven or eight of molar 
teeth. The latter differ from those of the preceding genera, 
and thereby resemble the corresponding lower teeth of the 
existing Opossums and Bandicoots, in that they consist of an 
anterior portion carrying three cusps arranged in a triangle, 
and of a posterior moiety, or heel. It has only quite recently 
been ascertained that the earliest known of all the Secondary 
Marsupials, namely, the Am/pAitherium ot Stonesfield, which was 
described by the French naturalist De Blainville as far back 
as the year 1838, had teeth of this type. 
The great interest attaching to Amphilestes, Amblotherium, 
Amphitherium, and their allies, is that they, and they alone 
among Mammals, had molar teeth comparable in form, and 
to a certain extent in structure, with those of the existing 
Banded Ant-eater (A/yrmecobius) of Australia, which, as already 
mentioned, may be regarded as the sole and specially modified 
descendant of these ancient forms of Mammalian life. 
Several genera allied to Amblotherium are represented in the 
upper Jurassic rocks of North America; amongst them one 
which has received the name of Dryolestes may be specially 
mentioned ; and it appears that in that continent certain 
members of the families survived till the succeeding Creta- 
ceous epoch. 
FAMILY DROMATHERIID. 
GENUS DROMATHERIUM. 
Dyromatherium, Ernmons, American Geology, pt. vi., p. 93, 
5o57. 
The earliest, and at the same time the most generalised 
