MAMMALIA. 303 
row in the ground (Fig. 328). An extinct wombat as 
large as a tapir has been found in Australia, The wom- 
bats are valued as food. Allied are the phalangers, the 
koala that carries its young on its back (Fig. 327), and 
many others. 
Fic. 328.—Tasmanian marsupials. 1, wombats; z, Tasmanian devil; 3, 
Tasmanian wolf. 
_ Sub-Class III.—Monopevputa (Placental Mammals). 
General Characteristics.—In this sub-class are included 
all the rest of the mammals. They are called placental 
because the young, which are larger when born than the 
preceding forms, and generally perfect, are nourished 
up to the time of birth by a vascular membrane, pene- 
trated by veins and arteries, known as the placenta. 
Order I. Edentata (toothless). General Character- 
éstics.—The animals of this family have no incisor teeth, 
some being entirely toothless. In some, scales take the 
place of hair. 
