PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
267 
character in Phascolagus and Sthenurus appears in Boriogale, where the nerves and vessels, 
passing by the floor of the orbit to the maxilla, leave only one mark of perforation of that 
floor by a subcircular entry to the canal, the other elements forming the second and con- 
tiguous foramen in Macropus, &c„ here traversing the above-surmised membranous 
or unossified state of the inner and under wall of the orbit. The reduced ossified part 
continued from above the bony canal rises somewhat like the lamellate process shown 
at n, figs. 4 & 5, in Sthenurus. Boriogale also shows the longitudinal depression above 
and exterior to the entorbital foramen, terminating anteriorly in a blind end, as is seen 
in Sthenurus and in a feebler degree in Halmaturus. 
The outlet of the suborbital canal in Sthenurus Atlas is relatively further from the 
orbit than in Macropus major , in which respect the present fossil resembles Osphranter 
and Halmaturus : the distance in the present example of Sthenurus Atlas is 1 inch 1 line. 
The lower part only of the outlet and canal is preserved in the present specimen ; and 
below the outlet is a second small foramen, the canal from which passes backward, not 
downward as in Macropus Titan. 
There is not sufficient of the bony palate preserved to determine whether it was as 
entire as in the larger living Kangaroos ( Macropus major, Osphranter robustus, Phasco- 
lagus erubescens), or with vacuities, as in most species of Halmaturus ; but part of the 
border opposite the interval between d 4 and m i (Plate XXIV. fig. 6) is so smoothly 
rounded off as to suggest that it is a natural, not a broken, tract. 
The premolar has the middle two fourths of its outer surface slightly depressed and 
feebly concave lengthwise (ib. figs. 4 & 6, a), with two chief vertical ridges and others 
faintly indicated. The fore and hind ends of the outer surface are smooth and 
convex, or bulging; the free margin is subtrenchant, with the ends of the terminal 
bulges obtuse. The inner surface or division of the'crown (ib. fig. 5, b) is much lower 
than the outer one, yet having more of the character of a part of the crown than of a 
developed “ cingulum it increases in height as it recedes, the hind part swelling into 
an inner lobe, continued at the back part of the crown into the postexternal tubercle 
and abutting against the inner side of that part by a second transverse ridge. The 
lower and less developed fore part of the inner division of the crown is similarly con- 
nected with the antexternal tubercle, viz. by a low ridge forming the fore part of the 
crown, and by a buttress-like production against the inner surface of that tubercle. 
The intermediate part of the inner division is connected with the outer division by three 
transverse ridges (ib. fig, 6 ,p 3), A premolar of the size shown in the figures, and with 
the structure above described, would be held, according to its proportions to the molars 
behind, as indicative of a subgeneric section of Macropodidce, for which I propose the 
term Sthenurus , suggested by the form and proportions of a vertebra of the very powerful 
tail of this great extinct Kangaroo*. I shall presently be able to show that the modi- 
fications of the mandible and mandibular incisor support this distinction. 
The bilophodont upper molars of Sthenurus are characterized by a narrow prebasal 
* Gr. irdevos, strength ; oifii, tail. 
