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PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
show modifications in the size, form, structure, and order of succession and shedding of 
teeth requisite for the description and comprehension of characters of fossil jaws and 
teeth of the present family of Marsupials. 
Thus, in Macropus (Osphranter) robustus, Gd. (Plate XX. figs. 13 & 14), the premolar 
(p 3 ), which is not larger than that in Macropus major*, is later retained; and the following 
molar ( d 4 ) in my subject had undergone a much greater degree of wear than in Macropus 
major before p 3 had risen into place. This is plainly shown by the lower level of the 
much -worn d 4 in fig. 1 3. It would also seem to have been originally a relatively smaller 
tooth than its homologue in the “ greater Kangaroo.” The last molar is in place, and 
shows the same slight degree of masticatory wear in both species ; but with this the 
molar series is reduced to four teeth in one, and shows five teeth, or four and a half, in 
the other. 
In Macropus ( Halmaturus ) ualabatus, Less. & Gd. (Plate XX. fig. 11), the premolar 
(p 3), which is relatively larger than in the two preceding Kangaroos, has risen into place 
before the crown of the following molar ( d 4) was worn down to its base. The hinder 
thickened end of p 3 is worn nearly level with the more complex grinding-surface 
of d 4, which nevertheless indicates, by the extent of exposed dentine, that it had 
been in use when the deciduous predecessors ( d 2 and d 3) of the premolar (p 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 ( Halmaturus ) rujicollis. Dm., Gd.) (Plate XX. 
figs. 9 & 10) the penultimate molar (m 2 ) is in place and use before the first two deci- 
duous molars (d 2, d 3) 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 Halma- 
turus rujicollis, Gd. ( Kangurus rujicollis. Dm., 1817), is that of H. ualabatus. 
In Macropus ( Halmaturus ) erubescens, Scl.f, the premolar (Plate XX. figs. 1-8, p 3) 
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 
* Anat. of Vertebrates, vol. iii. fig. 296, e, p 3. 
f 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 Halmaturus of Mr. Waterhouse’s arrangement.” But the bony palate is entire, as in most large 
Kangaroos, including M. antilopinus, M. robustus, and M. rufus “ of the present convenient but, as it appears 
to me, arbitrary division ” (Waterhouse, op. cit. p. 95). 
