184 



PEOFESSOE OAVEN OX THE FOSSIL MAM:\IALS OF ATJSTEALIA. 



lomys pIafijr1dnus,Q.ndi 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. h, h)^ 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 IlitchelH (Plate XVIII. figs. 1-4), from freshwater 

 deposits, resembles Phase, plafyrhmus 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 s) indicates the same position of the groove. In Phascolomys latifrons the 

 fore part of d z (Woodcut, fig. 8) is less produced than in Phase. ])latyrlnnus 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 W^ombats 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 

 maxillaiy 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. 



Tlie 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. 25) 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 vomhatus 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 tlic 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 AVombat, 

 with all the molars in place and use, the series is 1 inch 7 lines. 



* Trans. Zool. Soc. vol. ii. (1838) plate Ixxi. fig. 0. 



