:;os 



which is relatively larger than in the two preceding Kangaroos, has risen into place 

 before the crown of the following molar (d i) was worn down to its base. The hinder 

 thickened end of p 3 is not worn level with the more complex grinding-surface of d 4, 

 which, moreover, indicates, by the extent of exposed dentine, that that tooth had been 

 in use when the deciduous predecessors (d 2 and d 3) of the premolar (/> 3) were in place. 

 The last molar is here fully developed ; its front lobe is abraded, and the series of five 

 teeth are in a condition to continue together the work of mastication for a great part, 

 at least, of the lifetime of this smaller kind of Kangaroo. 



In the Red-necked Kangaroo (Macropus (Ilahnaturus) ruficollis, Dm., Gd.) (ib. figs. 9 

 & 10) the penultimate molar (1112) is in place and use before the first two deciduous 

 molars (d 2, d 2) are shed, and when the premolar (p 3) is concealed, with the two roots 

 as yet unformed, in its cell of development. The crown of the last molar (m 3) is also 

 formed, and was about to pierce the gum. The permanent dentition of Ilahnaturus 

 nificollis, Gd. (Kangurus rujicollis, Dm., 1817), is that oi II. ualabatus. 



In Macropus (Ilahnaturus) erubescens, Scl.*, the premolar (ib. figs. 1-8, p z) has, in 

 the upper jaw (fig. 1), nearly risen into place, the crown being extricated from the 

 formative socket before the penultimate molar has appeared through the gum. The 

 skull here figured gives an interesting phase of dental development. The premolar has 

 displaced the second deciduous molar (d 3) on both sides of the upper jaw, d 2 continuing 

 on the left side, and its socket being unobliterated on the right side. In the lower jaw 

 (fig. 4) the premolar (p 3) has pushed half its crown above the socket on the left side, 

 from which both d 2 and d 3 are displaced, whilst d 3 remains on the right side, the premolar 

 not having come into view ; a trace of the socket of the shed d 2 remains. In a younger 

 individual of Macropus erubescens, the skull of which, marked " ' Uroo,' far north," was 

 kindly sent to me from Adelaide, South Australia, by G. F. Waterhouse, Esq., the three 

 deciduous molars are in place and use (Plate LXXX. figs. 6 & 7, d 2, d 3, d 4); m 1 has 

 nearly risen into place in the upper jaw (fig. 6), but is not so far advanced in the lower 

 jaw (fig. 7). The germ of the premolar (p 3) is exposed by removal of bone in the upper 

 jaw. 



In the skull of a nearly full-grown Kangaroo (Macropus (Boriogale) magnus, Ow.), 

 also from the " far north " of the province of South Australia, the premolar is represented 

 by the foremost deciduous tooth. On the left side of the upper jaw it is in contact with 

 (I 1, and W3 is nearly risen into place; on the right side (ib. fig. 12) a vacuity corre- 

 sponding with the hind half of d 3 remains, and shows the socket of the hind root of 

 that deciduous tooth. Its homotype in the lower jaw (fig. 12 a) is shed in both rami, 

 and the very small bilobed crown of d 2, or p 3, is in close contact with d 4. If d 2 had a 



* Sclater, « Proceedings of the Zoological Society,' March 7th, 1871, p. 240 (Cut, figs. 5 & 6). This eminent 

 zoologist remarks : — " The muffle of M. erubescens is quite naked ; and the species therefore belongs strictly to 

 the section Hahnaturus of Mr. Waterhotjse's arrangement." But the bony palate is entire, as in most large 

 Kangaroos, including 31. antilopinus, M. robustus, and M. rufus " of the present convenient but, as it appears 

 to me, arbitrary division " (Waterhouse, op. cit. p. 95). 



