746 MAMMALIA, 
sets are defined by the characters of the teeth, which are, of course, 
adapted to habit. In the members of the first sub-order the incisors 
are numerous (not less than 4), small, and almost equal in size ; while 
the canines are large, and the molars furnished with sharp cusps. The 
whole dentition presents a striking resemblance to that of the Eutherian 
Carnivores. To this group the name Polyprotodontia is applied, and 
the forms included in it are typically carnivorous or insectivorous. The 
ceecum is absent or very small. 
In the remaining families the incisors are usually 3 in number, and 
those above are of unequal size, the centre ones being largest. The 
canines are usually small or absent; the molars are furnished with 
blunt tubercles, or transverse ridges. To these typically herbivorous 
forms the name Diprotodont is applied ; they are more highly special- 
ised than the Polyprotodonts, and are more modern. 
A, POLYPROTODONTIA 
1, Family Didelphyidee.—American opossums, distributed from the 
United States to Patagonia, arboreal in habit, usually carnivorous 
or insectivorous in diet. The limbs have five clawed digits ; 
the hallux is opposable. The tail is generally long, and often 
prehensile. The stomach is simple; the cecum small. The 
pouch is generally absent, but the young are often carried on 
the back of the mother, their tails coiled round hers. Dentition, 
5134 
eG 
Examples: The Virginian or crab-eating opossum (Didel¢hys 
marsupialis), with a pouch ; the woolly opossum (D. /azigera) ; 
the aquatic Yapock (Chzronectes), which feeds on fish and 
smaller water animals. 
2. Family Dasyuridee.—Carnivorous or insectivorous Marsupials. The 
limbs have clawed digits, five in front, four or five behind. The 
canines are generally large. The stomach is simple; there is 
no czecum. 
Examples.—The Tasmanian wolf (Zhy/acinus), of dog-like form, 
dentition a and the Dasyure (Dasyzrus), civet-like, den- 
tition Pl are specialised as carnivores. The members of the 
genus Phascogale are small and insectivorous. The banded 
ant-eater (AZyrmecobius) of W. and S. Australia, 2 somewhat 
squirrel-like animal, has a long thread-like protrusible tongue, 
and more teeth than any other Marsupial, oe It differs 
markedly from the other members of the family. 
3. Family Notoryctida.—This family has been erected for the mole- 
like Marsupial (Motoryctes typhlops), found in the sandy deserts 
of S. Australia. It lives underground, is a rapid burrower, and 
in its rudimentary eyes, keeled sternum, and some other respects, 
