262 
PROFESSOR. OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
lower one in the type mandible of Macropus Titan (Plate XXII. fig. 18) than does the 
premolar exposed in the specimen under examination (Plate XXII. fig. 1). 
These phases of dentition, illustrative of the characters and affinities of the fossil 
under review, are shown in the specimens Nos. 1741, 1742, and 1743, in the Osteo- 
logical Series of the Museum of the Eoyal College of Surgeons of England*, and are 
illustrated in Plate XX. figs. 1-12 of the present Paper. In the recent species ( Macropus 
(Phascolagus) erubescens) the upper premolar (ib. fig. 6,p s), in its form and proportions, 
still more closely resembles that (Plate XXII. fig. 1 ,p 3) of the larger extinct Kangaroo 
( Phascolagus altus ) of the Wellington Valley Bone-cave. 
This species combines with the proportion of the premolar, affording one of the cha- 
racters of the subgenus Halmaturus , the entire or imperforate bony palate, which is 
found in all the species of Macropus in its restricted or subgeneric sense (Plate XXII. 
fig. 2). In this combination of characters the fossil agrees with the existing Phascolagus 
erubescens. 
The degree of development of the concealed premolar, the crown being completed 
with the basal portions of both roots, coincides, as in Phascolagus erubescens , with the 
incompleted eruption of the molar (m 1) and the still hidden and undeveloped state of 
m 2 and m 3 ; whence may be inferred a like precocious appearance of the premolar in 
the working series, with the concomitant shedding of the two anterior deciduous teeth 
(d 2, d 3), the premolar preceding the penultimate molar in entering upon the work of 
mastication. The differences observable between the fossil and the recent Kangaroos 
combining the above characteristics of the proposed subgenus are, at least, specific. 
The premolar, divided in both by a vertical cleft into a smaller anterior and a larger 
posterior lobe, shows in the fossil a more definite basal ridge along the outer side of the 
latter lobe than in Phascolagus erubescens ; there is also a more definite outswelling of 
the hind part of the hind lobe in Phascolagus altus ; two feeble grooves divide the 
outer surface of the fore part of the anterior lobe into three vertical prominences, but 
these are faintly marked in the present fossil. 
In the bilophodont molars the prebasal ridge is narrow and the indication of the fore 
link is minute. The mid link is narrow, neatly defined, and sinks rapidly from the 
inner and posterior apex of the front lobe to the lower part of the interlobal valley. 
The postbasal ridge is represented by a similar outbending and descent of a sharp 
ridge from the inner angle of the hind lobe ; which ridge, curving to subside upon the 
outer part of the base of the hind lobe, circumscribes, below, the depression or trans- 
verse concavity on the hind surface of that lobe. 
The position and extent of the origin of the anterior pier of the zygoma is the same 
in the fossil and the recent species compared. The configuration of the hind margin 
of the bony galate is the same. But our extinct Kangaroo shows these characters of 
its subgenus on a larger scale than the largest known existing species of Phascolagus. 
The tooth d 4 (Plate XXII. fig. 2) is as large as its homologue in Macropus major ; the 
* Osteological Catalogue, 4to, 1853, p. 324. 
