There is but one species, the Koala or Native Bear of the Australian colonists (_P. cinereus_), an animal of comparatively large size and heavy build (Fig. 50), found in the south-eastern parts of the Australian continent. It is about two feet in length, and of an ash-gray colour, an excellent climber, and residing generally in lofty _Eucalyptus_ trees, on the buds and tender shoots of which it feeds, though occasionally descending to the ground in the night. EXTINCT PHALANGEROIDS. Numerous imperfect remains recently described by De Vis are regarded as indicating large extinct types of _Phalangeridæ_, but further evidence is required before all these determinations can be definitely accepted. Thus part of an upper jaw is provisionally referred to a large species of _Pseudochirus_, while part of a scapula is made the type of a genus _Archizonurus_ which appears to be allied to the former. Another fragmentary scapula is considered to indicate a large _Phalanger_. Finally, part of a fibula, described under the name of _Koalemus_ is regarded as affording evidence of the former existence of a large ancestral form allied to the Koala, and it is suggested that an upper jaw with teeth may belong to the same or an allied type. [Illustration: FIG. 50.—The Koala (_Phascolarctus cinereus_). From Sclater, _Proc. Zool. Soc._ 1880, p. 355.] _Thylacoleo._[67]—Dentition of adult: _i_ ³⁄₁, _c_ ¹⁄₀, _p_ ³⁄₃, _m_ ¹⁄₂; total 28. First upper incisor much larger than the others; canine and first two premolars rudimentary. In the lower jaw the two small anterior premolars are functionless, and often deciduous; posterior premolars of both jaws formed on the same type as those of _Potorous_, but relatively much larger; true molars rudimentary, tubercular. One species, _T. carnifex_. This animal presents a most anomalous condition of dentition, the functional teeth being reduced to one pair of large cutting incisors situated close to the median line, and one great, trenchant, compressed premolar, on each side above and below. It was first described as a carnivorous Marsupial, and named, in accordance with its presumed habits, “as one of the fellest and most destructive of predatory beasts”; but, as its affinities are certainly with the _Phalangeridæ_ and _Macropodidæ_, and its dentition completely unlike that of any known predaceous animal, this view has been called in question. [Illustration: FIG. 51.—Front view of skull of _Thylacoleo carnifex_, restored. ¹⁄₃ natural size. From _Quart. Journ. Geol. Soc._ vol. xxiv. p. 312.] The dentition is nearer to that of the existing _Phalangeridæ_ than to that of the _Macropodidæ_, and the genus may be provisionally regarded as the type of a distinct subfamily of the former. _Family_ MACROPODIDÆ.