502 CHORDATA. 
characters, be recognised at once by the presence of more 
than three pairs of upper incisors. The canines are large 
and prominent and the molars are cusped. In other words, 
the Polyprotodontia have a typical carnivorous dentition, and 
all are flesh- or insect-eaters. They are aquatic, cursorial, 
fossorial, or arboreal. 
Family I.—Didelphidz comprise the Ofossums, found in the 
warmer regions of America. They are usually ‘‘true arboreal” and 
hence have an opposable hallux or big toe, the other four toes being 
nearly equal and each bearing a claw. The Yapock, however, is 
aquatic and has webbed feet. The opossums vary in size and colora- 
tion and there is a large number of species. 
Fig. 347._JAWs AND TEETH OF THE OpposuM (Didelphys). 
Note the five upper and four lower incisors, long canines, sharp cusped molars 
with four true molars (234). An essentially carnivorous dentition. 
4134. 
Family II.—Dasyuridz comprise a number of carnivorous and 
insectivorous animals found in the Australian region. They vary in 
size from the Tasmanian wolf ( 7hylacinus) to the little mouse-like 
Phascogale. The Tasmanian ‘‘devil” (Sarcophilus) has the fossorial 
habits of the badger, and the Dasyures (Lasyurus ) are much like small 
civets. The Banded Anteater (Wyrmecobius) has a great number of 
small teeth and it has no pouch. 
Family IIJ].—Peramelidz comprise a number of small animals, 
the Bandicoots, found only in the Australian region. They are ‘‘ small- 
flesh” eaters (worms, insects and occasionally vegetable diet). 
They are interesting for two structural features, viz., the presence of 
an allantoic placenta and the syndactylic condition of the hind-foot (see 
Diprotodontia). The ‘‘ Native Rabbit” ( Peraga/e ) is fossorial. 
Family IV.—Notoryctidz is made for the curious metatherian 
mole (Motoryctes). A true fossorial type found in the sandy districts 
of centrai Australia. Its structure is adapted for rapid bunowing 
and in this respect shows a likeness to the fossorial armadillos and 
to the mole. 
