said that 15 or even 20 feet are covered at a bound, and in bound after bound. But in walking slowly it can be readily seen from an inspection of Kangaroos at the Zoological Society's Gardens that the animal does rest upon its tail, which with the hind-legs forms a tripod. _Petrogale_ with six species comes next to _Macropus_, and is indeed only to be differentiated from it by the thickly-haired and more slender tail, which is not used, as it is sometimes in the Kangaroos, as an extra hind-limb. The Rock-Kangaroos live among rocks, which they climb, and from which they leap; and the tail acts rather as a balancing pole. The most elaborate account of the anatomy of _Petrogale_ known to me is by Mr. Parsons.[79] The dentition as given by Mr. Thomas is I 3/1 C 0/0 Pm 2/2 M 4/4--that of _Macropus_ without the occasionally occurring canine of the upper jaw. The osteological characters which separate it from _Macropus_ are quite insignificant. Mr. Parsons mentions a wormian bone, "os epilepticum," at the junction of the coronal and sagittal sutures. It was found to occur in two out of five skulls examined, and appears not to occur in other Kangaroos. The palatine foramina of _Petrogale_ are so large that the posterior part of the bone is only a narrow thickened ridge. The small intestine of _P. xanthopus_ is 102 inches long, the large intestine 44 inches. The caecum has a length of 6 inches, and is not sacculated, differing in this from the caecum of _Macropus major_. The best known species are _P. xanthopus_ and _P. penicillata_. The genus is confined to Australia itself, and does not enter Tasmania. _Onychogale_ includes the so-called "Nail-tailed Wallabies," which have a thorn at the end of the tail, reminding one of the Lion and the Leopard, whose tails have a similar armature. The muffle is hairy. Three species are allowed by Mr. Thomas. _Lagorchestes_ has, like the last genus, the rhinarium, _i.e._ that part of the nose immediately surrounding the nostrils, hairy instead of smooth as in the Kangaroos proper. It is distinguished from _Onychogale_ by the absence of the terminal callosity to the tail, which is rather short. The name Hare-Kangaroo is given to the members of this genus (three species) on account of their exceeding fleetness. This genus is limited to Australia itself. _L. conspicillatus_ is said to present "a remarkable {135} resemblance to the English hare," and _L. leporoides_ was so called by Gould on account of general appearance as well as face. _Dorcopsis_ has shorter hind-legs than _Macropus_, and a naked muffle. The ears are small. The structure of _D. luctuosa_ has been studied by Garrod,[80] who pointed out the existence of four enlarged hair follicles on the neck near the mandibular symphysis. These are, however, represented in the next genus _Dendrolagus_, and occur also in _Petrogale_. The limbs are not so disproportionate as in _Macropus_, and the tail is naked at the tip.