MARSUPIALS. 575 
they are attached to the nipples at the bottom of the pouch. 
This large pouch (absent in some opossums and in the 
Dasyuride) is supported by two long slender bones attached 
to the front edge of the pelvis and projecting forward (Fig. 
495 m and Fig. 497). 
In Thylacinus, the ee wolf, these bones are car- 
tilaginous. In the opossum, the kangaroo, and probably 
most marsupials, the young remains in the pouch attached 
to the nipple, which fills the mouth. ‘‘ To this it remains at- 
tached for a considerable period, the milk being forced down 
its throat by the contraction of the cremaster muscle. The 
danger of suffocation is avoided by the elongated and coni- 
cal form of the upper extremity of the larynx, which is em- 
braced by the soft palate, as in the Cetacea, and thus respi- 
ration goes on freely, 
while the milk passes, 
on each side of the 
laryngeal cone, into 
the esophagus” 
(Huxley). In the car- 
nivorous forms the 
brain is low in struc- 
ture, the olfactory 
lobes being very large, 
completely exposed, 
while the cerebral 
hemispheres are small Fr Oa ra perp ence g 
and quite smooth. 
The dentition of marsupials is characteristic, none having 
three incisor teeth upon each side, above and below, and 
none but the wombat (Phascolomys), with an equal num- 
ber of incisors in each jaw, there being usually more in the 
upper than in the under jaw. 
The lowest marsup:al is the Tasmanian wolf (Thylacinus), 
which is rather smaller than the wolf. The Tasmanian devil 
(Dasyurus ursinus Geoffroy, Fig. 383) isa vicious, trouble- 
some creature, about the size of a badger. The opossums 
inhabit North and South America. They have a long tail 
and a plantigrade step—i.e., they walk on the sole of the 
whole foot, The Virginian opossum (Fig. 497, Didelphys Vir- 
