25 4 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
aperture of the antorbital canal, and a considerable extent of the bony palate (showing 
the same imperforate structure as in the preceding specimens of Macropus Titan). 
The pier of the zygoma extends obliquely from the under and fore part of the orbit 
downward and backward, the hind border being on the vertical parallel of the middle of 
the last molar. The ridge from the outer side of the masseteric process subsides, as it 
rises toward the orbit, sooner than in Macropus major or Macropus lanicjer. As in the 
last described specimen, the anterior outlet of the suborbital canal is relatively further 
in advance of the orbit than in Macropus major , being ah inch from that part and on a 
vertical parallel with the diastema in advance of the front molar (d 4) ; in Macropus 
major it is above the interval between d 4 and m 1 , and opens only 4^ lines in advance 
of the orbit. In Osphranter robustus,G d., the antorbital foramen is 10 lines in advance 
of the nearest part of the orbital margin, and is on the vertical parallel of d 4. It thus 
more nearly resembles Macropus Titan than does Macropus major ; but the larger 
extinct Kangaroo differs from both the large existing species in the following structure, 
which I now have ground for regarding as constant. There is, as observed in former 
fossils of Macropus Titan , a foramen (a) 3 lines behind the antorbital one ( 21 ), fig. 10 ; it 
is not another outlet of the suborbital canal, but leads obliquely downward into the 
entrance or substance of the maxillary bone. Of this foramen (a) I have not seen a trace 
in any existing Kangaroo, save Macropus erubescens (Plate XX. fig. 1, a). The degree of 
attrition of the upper molars in fig. 11, Plate XXII., agrees with that of the lower molars 
in fig. 14, ib. The exposed tract of dentine in d 4 is continuous, the mid link being 
worn down to its base ; the fore part of the crown is broken off. In m 1 the front lobe 
is worn down to the level of the prebasal ridge, which is well marked, overlies the back 
part of d 4, and shows a rudiment of a link or mid rising to the front lobe of its own 
tooth. The line of abrasion of this lobe is from without inward and a little back- 
ward, not transverse to the skull’s axis : a mid link is continued from it to the middle 
of the front surface of the hind lobe ; this is worn, but not so as to obliterate the 
oblique outer cleft dividing it from the postbasal ridge which rises to he lost in the 
inner end of the hind lobe. 
In m 2 the characteristic configuration of the crown of the upper molar of Macropus 
Titan is well shown. The two chief lobes are more nearly transverse in the direction 
of their summits than in Macropus major ; the prebasal ridge with its linking process 
and the mid link are as well marked as in that species, and the oblique postbasal ridge 
is longer. In the last upper molar of Macropus Titan this ridge ( g ), which is almost 
obsolete in Macropus major , is as well marked as in the preceding molar, m 2. The 
mid link of the last molar is more curved than that of m 2 ; the concavity of the curve 
is turned inward. 
Compared with the molars of Sthenurus Atlas (Plate XXIV. fig. 6) the prebasal 
ridge is rather more developed, the mid link is thicker, the outer and inner sides of the 
transverse ridges are thicker and more prominent, and the fore-and-aft extent of the crown 
is relatively greater. 
