PKOFESSOR OWEN ON THE EOSSIL MAMMALS OF AUSTEALIA. 



181 



does the other two recent species is the greater vertical extent of the maxillary (Plate 

 XVII. figs. 3 & 4, 2i«) beneath the origin of the malar or zygomatic process (ai*) of that 

 bone (compare with Cuts 5 «&; 6, 2i«), I shall recur to this character in the description 

 of another fossil of the present genus. 



§ 8. Upper molars o/Phascolomys Mitchelli, Ow. — The differential characters of these 

 teeth, as compared with their homologues in Phascolomys vombatus, have been elsewhere 

 pointed outf . As to the two larger existing species, in the molar dentition of the upper 

 jaw Fhascolomi/s Mitchelli more resembles the platyrhine than the broad-fronted Wombat. 

 In the latter the right and left upper molar series (Woodcut, fig. 8, d s-m s) run more 

 parallel to each other, are less convergent anteriorly, with absolute greater breadth 

 of the bony palate there. The first molar (d 3) in Phascolomys latifrons is, relatively to 

 the second, larger in both upper and under jawsj. I therefore limit the comparison of 

 the upper molars in the present fossil to those of Phascolomys platyrhinus (fig. 7, d 3-m 3). 

 The extent of the five alveoli, lengthwise, taken at their outlets, is the same in botli ; 

 or at least the fossil (Plate XVII. fig. 5, d a-m 3) exceeds only by about a line, giving 

 2 inches 2^ lines instead of 2 inches 1 line as in Phascolomys platyrhinus. I have seen 

 no example oi Phascolomys latifrons in which the molar series extended beyond 2 inches ; 

 it is commonly less, as in Woodcut, fig. 8. 



The alveolus of the first molar ( ^ 3) of the fossil indicates a tooth not larger than in 

 the Platyrhine Wombat. The other four molars, of which the first three are preserved 

 on the left side and the last two on the right side, closely repeat the characters of these 

 teeth in the Platyrhine Wombat §. This gives more weight to the difi"erential characters 

 of greater length and less breadth of the nasals, the greater concavity and sharper defi- 

 nition of the diastemal part of the bony palate, and the greater depth of the maxillary 

 below the anterior pier of the zygomatic arch in Phascolomys Mitchelli. 



§ 9. Palatine foramina in Phascolomys. — I next proceed to notice Phascolomydian 

 fossils from the freshwater deposits of Queensland, in the interpretation of which some 

 observations must be premised on the palatal foramina in existing species of Wombat. 



In my first paper on the Osteology of the Marsupialia I state that Phascolomys resem- 

 bles Phascolarctos and Hypsiprymnus in having " the posterior palatal openings large 

 and situated entirely in the palatal bones ; and that posterior and external to these are 

 two small perforations" ||. In the other two species [Phascolomys latifrons and Phasco- 

 lomys platyrhinus) determined by cranial characters since the date of that remark (1838), 

 the generic characters of the postpalatal openings are repeated. These additional mate- 

 rials serve to test the statement that in Marsupials " the perforations of the bony palate 



t Mitcitell's ' Three Expeditions into the Interior of Eastern Australia,' vol. ii. p. 368, pi. 48. See also 

 Waterhouse, ' Natural History of the MammaHa,' 8vo, 1845, p. 244. 

 + Loc. cit. p. 304. 



§ The second molar is abnormally worn, through slight displacement of the opposing tooth, as happens in 

 other partiallj'' enamelled teeth of perpetual growth. 



II '•' On the Osteology of the Marsupialia," Trans. Zool. Soc. vol. ii. p. 389. 

 MDCCCLXXII. 2 B 



