327 



In the extent, especially hinder breadth and feeble concavity, of the bony palate, Phas- 

 colomys plat yrhinus most resembles the present (ib. fig. 7) as it does the preceding fossil ; 

 but the zygomatic character only stands out the more strongly in connexion with this 

 resemblance and the general size. 



In Phascolomys vombatus the form of the palate resembles that in Phascolomys pla- 

 tyrhinus. It is rather more concave in some individuals than in others in both species ; 

 and in the Platyrhine Wombat I have noticed a slight mesial ridge along the bony palate. 



In Phascolomys latifrons the palate is not only more concave, but is wider anteriorly, 

 less triangular ; and at the hind part formed by the proper palatine bones, their median 

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

 or longitudinal channels, leading backward to the postpalatal apertures. 



§ 11. Mandibular characters of existing Wombats. — In differentiating by cranial 

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

 it with Phascolomys vombatus, 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 

 higher 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 platyrhinus, except that the coronoid process rises higher in the platyrhine 

 species (Plate LII. 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 

 from 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 LIIL, LIV. & LV. I, s') of the long symphysis (ib. s, s') is 

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

 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 1\ lines (Plate LV. fig. 2), in the other 1 inch 6^ lines; the breadth of 

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



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

 extent (Plate LIV. fig. 1), the diastema (I, 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 first mandible 8 lines, in the second 7 lines. 



* "On the Osteology of the Marsupialia" (Part II.) (1845), in Transactions of the Zoological Society, 

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



