Of the genus _Potorous_ there are three species, which are Tasmanian as well as Australian. Unlike the other Rat-Kangaroos, the hind-feet are comparatively short, and the animal is therefore less addicted to jumping than its relatives. The rhinarium is naked, and the ears are of fair length. SUB-FAM. 3. HYPSIPRYMNODONTINAE.--The Musk-Kangaroo, _Hypsiprymnodon_, is the last genus of the present family, and the only genus of this sub-family. It is intermediate between the Macropodidae and the Phalangeridae, the annectant character being mainly the hind-feet, which though they have the same long fourth digit as the Kangaroos, have it more feebly developed, and possess also an opposable hallux, which is one of the salient features in the structure of the Phalangeridae. The tail is naked and scaly; the rhinarium is entirely naked. The ears are large and not furry. The single species, _H. moschatus_, appears to feed upon insects as well as vegetables. "Its habits are chiefly diurnal, and its actions when not disturbed by no means ungraceful. It progresses in much the same manner as the Kangaroo-Rats (_Potorous_), to which it is closely allied, but procures its food by turning over the debris in the scrubs in search of insects, worms, and tuberous roots, frequently eating the palm berries, which it holds in its fore-paws after the manner of the Phalangers, sitting up on its haunches, or sometimes digging like the bandicoots." This is Mr. Ramsay's description of the animal, which he was the first to discover.[88] FAM. 2. PHALANGERIDAE.--The genus _Hypsiprymnodon_ bridges over the not very wide gap which separates the Kangaroos from the Phalangers. The Phalangers are Marsupials with five fingers and toes; the second and third toes are bound together by a {139} common integument as in the Macropodidae. The hallux is opposable and nailless. The tail is nearly always long and prehensile. The pouch is well developed; the stomach not sacculated; a caecum is present (except in _Tarsipes_). These are really the principal distinctions between the two families. In addition, it may be mentioned that the lower incisors have not a scissor-like action as in the Kangaroos. The Phalangers may be divided into four sub-families. The first of these, that of the PHALANGERINAE, contains the genera _Phalanger_ (including _Cuscus_), _Acrobates_, _Distaechurus_, _Dromicia_, _Gymnobelideus_, _Petaurus_, _Petauroides_, _Dactylopsila_, _Pseudochirus_, and _Trichosurus_. These genera agree in the following generalities:--Tail well developed, often very long; three incisors above, and at least two premolars both above and below; caecum long and simple; stomach without a cardiac gland; liver not very complicated by secondary furrows, with a distinct caudate lobe; the vaginal median culs-de-sac often coalesced; lungs with an azygos lobe. [Illustration]