ISO 



PROFESSOE OAYEX OX THE EOSSIL jMAAOIALS OF ATJSTEALIA. 



suture rises as a longitudinal ridge dividing the bony palate there into two concavities 

 or longitudinal channels, leading backward to the postpalatal apertures. 



§ 11. Jlandibi'.lar characters of existing Wombats. — In differentiating by cranial 

 characters the species of Wombat called Phascolomys latifrons, I noted, in comparing 

 it with Phascolomys vomhatus, that " the curve of the lower border of the lower jaw is 

 much deeper, the inner angle of the condyle is less produced, the coronoid process is 

 higlier and narrower, and the postsymphysial depression is almost obsolete in the Lati- 

 front Wombat"*. With the exception of the latter particular, which is variable in both 

 species, subsequently acquired skulls have confirmed the constancy of the above charac- 

 ters. They likewise serve to differentiate the mandible of Phase, latifrons from that of 

 Phascolomys platyrhimis, except that the coronoid process rises higher in the platyrhine 

 species (Plate XXII. fig. 2, c) than in the Tasmanian Wombat (ib. fig. 1, c); but the 

 broader proportion of the process as compared with that in the Hairy-nosed Wombat 

 (ib. fig. 3, c) is retained. The deeper curve described by the lower contour of the jaw 

 firom the neck of the condyle to the incisive alveoli, as shown in fig. 5, Plate xxxvii. of 

 the undercited volumef , is a constant and well-marked character of Phascolomys latifrons ; 

 so, likewise, is the less produced inner angle of the condyle, shown in fig. 7, c d, of the 

 same Plate. In both the Tasmanian and Platyrhine Wombats this angle is more pro- 

 duced and deflected. 



The diastemal part (Plates XIX., XX. &: XXI. I, s') of the long symphysis (ib. s, s') is 

 subject to some variety in existing Wombats. In two mandibles of Phascolomys jjlaty- 

 rhinus, in which the length of the series of molar alveoli is 2 inches 3 lines, that of the 

 interval between the first alveolus and the foremost angle of the symphysis is, in one 

 skull, 1 inch 7^ lines (Plate XXI. fig. 2), in the other 1 inch 6^ lines; the breadth of 

 the diastema, midway, is the same in both, riz. 10 lines. 



In a mandible of Phascolomys latifrons with the molar series of alveoli 2 inches in 

 extent (Plate XX, fig. 1), the diastema (/, s'), taken as above to the foremost point at 

 the interspace of the incisors, is 1 inch 6 lines ; in a second mandible with the molar 

 alveoli 1 inch 10| lines in extent, that of the diastema is also 1 inch 6 lines : the breadth 

 of the diastema, midway, is in the fii'st mandible 8 lines, in the second 7 lines. 



In the two mandibles of the Platyrhme Wombat compared, the diastema is slightly 

 convex both lengthwise and across ; it is traversed by a pair of shallow longitudinal 

 grooves, and is not sharply defined from the sides of the symphysis. In a third mandible of 

 the same species (Plate XIX. fig. 2, /, /) the defining ridges ai-e better marked, the trans- 

 verse convexity is less so ; and this part of the symphysis is rather longer and narrower 

 than in the other two mandibles. In these respects the third mandible approaches 

 nearer to Phascolomys latifrons; but it differs, as do the other mandibles of the same 

 species as well as those of Phase, vomhatus, in the larger, especially broader, incisive 

 alveoli, and in the oblique course of their upper margins from the mid line of the sym- 



♦ " On tlio Ostcolopj- of the ilarsupiolia" (Part II.) (1845), in Transactions of the Zoological Society, 

 vol, iii. p. 304, plate xxxvii. figs. 2 & 5. f Trans. Zool. Soc. vol. iii. 



