326 PROF. OWEN ON THE CLASSIFICATION 
Genus Phascolarctus. 
The absence of anomalous spurious molars and of inferior canines appears to be con- 
stant in the only known species of this genus. The dental formula in three of this 
. . . = + — 1 
species, (Phasc. fuscus Desm.,) is: Incisors = ; canines =) premolars = ; mo- 
lars —: — 30. 
The true molars are larger in proportion than in the Phalangers ; each is beset with 
four three-sided pyramids, the cusps of which wear down in age, the outer series in the 
upper teeth being the first to give way ; those of the lower jaw are narrower than those 
of the upper. The spurious molars are compressed, and terminate in a cutting edge ; 
in those of the upper jaw there is a small parallel ridge along the inner side of the base. 
The canines slightly exceed in size the posterior incisors ; they terminate in an oblique 
cutting edge rather than a point ; their fang is closed at the extremity ; they are situated, 
as in the Phalangers, close to the intermaxillary suture. The lateral incisors of the up- 
per jaw are small and obtuse, the two middle incisors are of twice the size, conical, 
subcompressed, beveled off obliquely to an anterior cutting edge, but differing essentially 
from the dentes scalprarii of the Rodentia, in being closed at the extremity of the fang. 
The two incisors of the lower jaw resemble those of the upper, but are longer and more 
compressed: they are also formed by a temporary pulp, and its ossification is accom- 
panied by a closure of the aperture of the pulp cavity, as in the upper incisors. The 
Koala therefore, in regard to the number, kind, and conformation of its teeth, closely 
resembles the Phalangers, with which it agrees in its long cecum, but the stomach has 
a cardiac gland as in the Wombat. The extremities of the Koala are organized for 
prehension ; each is terminated by five digits ; the hind feet are provided with a large 
thumb, and have the two contiguous digits enveloped in the same tegumentary fold ; 
the anterior digits are divided into two groups, the thumb and index being opposed to 
the other three fingers. The fore-paws have a similar structure in some of the small 
Phalangers ; it is very conspicuous in some of the Petaurists. The Koala, however, 
differs from the Phalangers and Petaurists in the extreme shortness of its tail and in its 
more compact and heavy general form. It is known to feed on the buds and leaves of 
the trees in which it habitually resides. 
Tribe IV. POEPHAGA. 
The present tribe includes the most strictly vegetable feeders ; all the species have a 
complex sacculated stomach and a long simple cecum. 
Guided by the modifications of the teeth we pass from the Koala to the Kangaroo 
