Dentition _i_ ³⁄₁, _c_ ⁰⁻¹⁄₀, _p_ ²⁄₂, _m_ ⁴⁄₄. Incisors sharp and cutting, those of the lower jaw frequently having a scissor-like action against one another; upper canine, if present, small. Penultimate premolar shed with the fourth milk-molar, which is molariform and long persistent. Molars wide, and either transversely ridged or bluntly tuberculate. Premolars and molars moving forwards in the skull as the age of the animal increases, this being most marked in the larger species. Masseteric fossa of mandible hollowed out below into a deep cavity walled in externally by a plate of bone, and communicating with the inferior dental canal by a large foramen. Hind limbs usually larger than the anterior ones, and progression generally saltatorial. Fore feet with five digits; hind feet syndactylous, the fourth digit being very large and strongly clawed; hallux usually absent. Tail generally long and hairy, occasionally prehensile; stomach sacculated. Pouch large and opening forwards. [Illustration: FIG. 52.—Skeleton of right hind foot of Kangaroo.] The _Macropodidæ_ or Kangaroos, taken as a whole, form a very well-marked family, easily distinguished from the other members of the suborder by their general conformation, and by peculiarities in the structure of their limbs, teeth, and other organs. They vary in size from that of a sheep down to a small rabbit. The head, especially in the larger species, is small, compared with the rest of the body, and tapers forward to the muzzle. The shoulders and fore limbs are feebly developed, and the hind limbs usually of disproportionate strength and magnitude, which gives them a peculiarly awkward appearance when moving about on all fours, as they occasionally do when feeding. Rapid progression is, however, performed only by the powerful hind limbs, the animal covering the ground by a series of immense bounds, during which the fore part of the body is inclined forwards, and balanced by the long, strong, and tapering tail, which is carried horizontally backwards. When not moving they often assume a perfectly upright position, the tail aiding the two hind legs to form a sort of supporting tripod, and the front limbs dangling by the side of the chest. This position gives full scope for the senses of sight, hearing, and smell to warn of the approach of enemies, from which these animals save themselves by their bounding flight. The fore paws have live distinct digits, each armed with a strong curved claw.