PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
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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 “ 4 TJrooJ 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 XX. figs. 6 & 7, d 2, d 3, d 1) ; mi 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 (^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 
d 4, and m 3 is nearly risen into place ; on the right side (Plate XX. fig. 12) a vacuity 
corresponding 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 
predecessor, it must then be the tooth (p 3) which I suppose it to represent. In either 
case the modification is rare, and, so far as I know, unique in the bilophodont section of 
Macropodidce : assuming the foremost tooth to be d 2, it repeats the condition and 
formula of the molar series in JDiprotodon and Nototherium. 
I shall not here carry further the account of the dental changes in living species of 
Kangaroos; but there are modifications of the grinding- surface and crown of the molar 
teeth which are useful in tracing out the affinities of extinct species. 
The premolar, like the foremost deciduous molar, has an antero-posteriorly extended 
crown, with a more or less trenchant margin, supported by two roots. The margin may 
be slightly thickened and obtuse posteriorly, with a still more feeble swelling anteriorly, 
and the crown may not show any other modification ; such is the very small lower pre- 
molar of Macropus ( Osphranter ) robustus, Gd. (Plate XX. fig. 13, p 3). In the upper 
jaw of this species the premolar (fig. 14', a, b), with an increase in antero-posterior and 
transverse extent, shows none in the vertical direction ; but the thickened fore part 
of the crown is divided by a notch from the rest of the trenchant border, and this by a 
smaller notch from the hind swellings ; moreover the base of the crown is produced 
inward, and this ridge swells out posteriorly. The fore-and-aft dimension of the upper 
premolar does not, however, exceed that of the adjoining molar, d 4. 
In Macropus {Boriogale) magnus (fig. 12) the upper premolar, or its representative, 
is not so long from before backward as the adjoining two-ridged molar. The anterior 
thickening is not marked off by a notch ; it is connected by a basal rising with the hinder 
thickening, and the intermediate rather depressed outer surface shows two faint vertical 
ridges. An inner basal ridge swells into a small tubercle posteriorly. 
In the lower jaw (fig. 12 a) the still smaller homotype has the crown transversely 
cleft to its base, and the hinder, somewhat larger lobe is thickest behind, with a feeble 
internal tubercle. 
The upper premolar of Macropus erubescens (ib. figs. 1 & 2, p 3 ) is similarly cleft, 
2 k 2 
