194 



PEOFESSOE OWEN OJs" THE FOSSIL MAMMALS OF AUSTEALIA. 



the smallest. The hinder half of the diastemal tract, above, is bounded by a ridge (/) on 

 each side, and is there transversely concave. The outlet of the dental canal (Plate XX. 

 fig. 6, v) is more advanced in position than in Phascolomys vombatus (Plate XXII. 

 fig. 1, v). The outer enamelled surface of the incisor is transversely or vertically convex, 

 curving uninterruptedly to the lower border of the tooth, as in the bare-nosed Wombats, 

 but with less relative breadth of the tooth than in those existing species. Sufficient of 

 the angle of the jaw is preserved to show the partial division of the large cavity formed 

 by its inward extension into the inner (d) and outer (e) angular depressions (Plate 

 XXIII. fig. 7). The base of the coronoid process (Plate XX. figs. 6 & 7, c) is 6 lines 

 in fore-and-aft extent ; in Phascolomys vombatus it is 11 lines. 



The well-marked characters of this small extinct species are satisfactorily repeated in 

 a second mandibular specimen, also of the left ramus, but more mutilated behind. It 

 retains, however, the anterior end entire ; and the incisor shows its worn surface (Plate 

 XIX. figs. 6 & 7, /). The vertical diameter of the incisor equals the long diameter of 

 the working-surface of the second molar tooth, d 



A third illustration of this diminutive species is likewise afibrded by a portion of the 

 left mandibular ramus ; it is a small portion, but includes the last tAvo molars and the 

 hind half of the antepenultimate molar. The base of the common plate of the coro- 

 noid and condyloid processes is in part preserved, with a broken beginning of the ecto- 

 crotaphyte ridge : these, with the postalveolar ridge and ectalveolar groove, repeat the 

 characters of the more complete ramus (Plate XX. figs. 6 8c 7). The size of both bone 

 and teeth is the same in all. The present fossil, by the well-worn crowns of the molars, 

 appears to be from an old individual. The formal characters are incompatible with a 

 reference of those of size to immaturity. 



All the specimens of Phascolomys parvus were in the Boydian Collection of fossils 

 from the Lacustrine deposits of King's Creek, Darling Downs, Queensland, purchased by 

 the British Museum, and are in the same mineralized condition as the remains of Uijjro- 

 todon in the same collection. 



I reserve for another communication the evidences of extinct "Wombats exceedins: in 

 size the existing species. 



Explanation op the Plates. 

 PLATE XVIL 



Fig. L Upper view of anterior portion of skull of Phascolomys MitchelU. 

 Fig. 2. Upper view of anterior portion of skull of Phascolomys Krefftii. 

 Fig. o. lliglit side view of anterior portion of skull of Phascolomys MitchelU. 

 Fig. 4. Left side view of the same skull. 

 Fig. 5. Under view of the same skull. 



Fig. G. Front view of the portion of skull of Phascolomys Krefftii. 



Fig. 7. I'ortion of left maxillary, I'liascolomys MitchelU. 



Fig. 8. Palatal surface and upper molars of Phascolomys MitchelU. 



