It is a curious fact that the two long lower incisors can be used after the fashion of a pair of scissors, or rather a pair of shears. Their inner edges are sharpened, and they are capable of some motion towards and away from each other; by their means grass is cropped. The stomach of _Macropus_ (and of other allied genera) is peculiar by reason of its long and sacculated character; the oesophagus enters it very near the cardiac end, which is bifid. Messrs. Schaefer and Williams[77] have shown that the squamous, non-glandular epithelium of the oesophagus extends over the greater part of the stomach, only the pyloric extremity and one of the two cardiac caeca being lined with columnar epithelium. The Macropodidae are clearly divisible into three sub-families, which are distinguished by marked anatomical characters. In the sub-family MACROPODINAE (including the genera _Macropus_, _Petrogale_, _Lagorchestes_, _Dorcopsis_, _Dendrolagus_, _Onychogale_, and _Lagostrophus_) there is no hallux, and the tail is hairy. The oesophagus enters the stomach near the cardiac end. The caecum when short has no longitudinal bands; the liver has a Spigelian lobe. The second sub-family, POTOROINAE or HYPSIPRYMNINAE (including the genera _Potorous_, _Aepyprymnus_, _Bettongia_, and {132} _Caloprymnus_), consists of smaller animals than the Macropodinae, which, however, resemble them in having no hallux, but a hairy tail. The oesophagus enters the stomach near the pyloric end of that organ. The caecum, though short, has lateral longitudinal bands. The liver has no special Spigelian lobe. The canines are always present, being rarely so in Macropodinae, and are usually well developed. The third sub-family, that of the HYPSIPRYMNODONTIDAE, is doubtfully referable to the family; it consists of but one genus _Hypsiprymnodon_, which is in many points more like a Phalanger than a Kangaroo. It has an opposable hallux and a non-hairy, but scaly, tail. It has canines in the upper jaw. [Illustration] FIG. 66.--Red Kangaroo. _Macropus rufus._ x 1/18.