MAMMALIA. 503 
DisTRIBUTION.—The Family of the Opossums is found 
extending throughout the American continent, except the 
extreme north. The other three families are found in 
Australia or the Australian district, including Tasmania and 
New Guinea. 
This present-day distribution of Polyprotodontia differs 
from that of the past. There are a large number of meso- 
zoic mammals found widely scattered in Britain, Europe, 
United States and elsewhere, which, mainly in their 
dental character, seem to resemble the modern Polyproto- 
dontia (especially Myrmecobius). These appear to indicate 
that the distribution of the Polyprotodontia was in these early 
times much wider than at present (cf Diprotodontia). 
Fig. 348.—INNER VIEW OF Lerr Ramus or Lower Jaw 
oF AMPHILESTES BRODERIPI. 
(From Flower and LyppDEker, after OWEN.) 
P ” 
€\12394 6 Bil 2 
1\al \ 
owe Dg : 
—— 
From the Stonesfield Slate. 
OrvER II.—D¢protodontia. 
The Diprotodontia are essentially herbivorous, and hence 
they have few chisel-shaped incisors, never exceeding # 
and in some cases being reduced to }. The incisors 
of the lower jaw never exceed one pair, hence the name of 
the order. The lower canines are always lost, and often the 
upper molars have not the sharp cusps of the Polyproto- 
dontia but have blunt tubercles more suited for crushing 
vegetable food. The limbs vary in character, but they 
always have the syndactylic hind-foot described in the 
kangaroo. (This feature is also found in the Peramefide.) 
Family I.—Macropodidz.—A large family of kangaroos and 
their allies. The kangaroo has been used as a type of metatherian 
skeleton. The hind-limbs and tail are enormously developed for 
