184 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
lomys plat yrhinus, ancl the inner ends of the two lobes are more sharply, or less obtusely, 
angular than is usual in that species. The difference both in this character and the 
breadth of the molars is also notable between the present and the first-described fossil ; 
but seeing the influence direction and degree of attrition have upon the size and shape 
of the grinding-surface of the molars, the differences noted may be within the limits of 
that influence. In the subject of Woodcut, fig. 7, d * had been abnormally abraded. 
The characteristic downbending of the hind part of the palatines, which forms a trans- 
verse bar (Plate XVIII. fig. 1, a) behind the postpalatal apertures (ib. b, b ), perforated 
at each end from behind forwards by a smaller aperture in the recent Wombats, is 
repeated in this present instructive fossil (ib. fig. 4, d , d ). 
This evidence of Phascolomys Mitclielli (Plate XVIII. figs. 1-4), from freshwater 
deposits, resembles Phase, 'platyrhinus in the depth and position of the antero-internal 
longitudinal groove of d 3 , which tooth is wanting in the cave fossil, although the socket 
(ib. fig. 5, d 3) indicates the same position of the groove. In Phascolomys latifrons the 
fore part of d 3 (Woodcut, fig. 8) is less produced than in Phase, platyrhinus and Phase. 
Mitchelli. 
A difference in the grinding-surface of the upper molars and in the intervening bony 
palate between the subjects of fig. 5, Plate XVII., and fig. 1, Plate XVIII. is appreciable ; 
but, as above remarked, the one may be due to a phase of attrition ; and, moreover, the 
outer side of the surface is slightly mutilated in fig. 5, Plate XVIII. ; whilst the variety 
in regard to a rising along the mid palatal suture in the Platyrhine Wombats warns 
against founding a specific distinction thereon. 
These characters are of the less consequence, since, where they are not preserved in a 
fossil, there may be others which allow of no such hesitation in regard to the specific 
distinction of the Wombats; as, e.g., in the case of that to which the fragment of skull 
about to be described belongs (Plate XVIII. figs. 5, 6, 7). It is a portion of the left 
maxillary with the bony palate intervening between the left and right molary series, the 
left series being in place (ib. fig. 7), the right represented by the second molar and the 
alveoli of the two following teeth : the extent of the left molary series at their issue 
from the alveoli is 2 inches 2 lines. 
The chief value of the present specimen is the character of the malar process of the 
maxillary (ib. fig. 5, 21), which is preserved with the beginning of the attached part of 
the malar (ib. ib. 26) on the left side, showing the malo-maxillary suture. To this help 
in the determination of fossils of the marsupial genus under consideration I was led by 
the following comparisons. 
In the largest of three skulls of Phascolomys vombatus available for the purpose, the 
left upper molary series, taken as in the fossil, does not equal 2 inches ; it falls short by 
nearly a line. In the specimen figured in my “ Osteology of the Marsupialia” *, it is 
1 inch 8 lines ; in the next in size it is 1 inch 10 lines ; in an evidently younger Wombat, 
with all the molars in place and use, the series is 1 inch 7 lines. 
* Trans. Zool. Soc. vol. ii. (1838) plate lxxi. fig. 6. 
