194 
PROFESSOR OWEN ON THE EOSSIL MAMMALS OE AUSTRALIA. 
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, cl 4. 
A third illustration of this diminutive species is likewise afforded by a portion of the 
left mandibular ramus ; it is a small portion, but includes the last two 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 & 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 parvvis 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 Di]_jro~ 
todon in the same collection. 
I reserve for another communication the evidences of extinct Wombats exceeding in 
size the existing species. 
Explanation of the Plates. 
PLATE XVII. 
Fig. 1. Upper view of anterior portion of skull of Phascolomys Mitchelli. 
Fig. 2. Upper view of anterior portion of skull of Phascolomys Krefftii. 
Fig. 3. Bight side view of anterior portion of skull of Phascolomys Mitchelli. 
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. Portion of left maxillary, Phascolomys Mitchelli. 
Fig. 8. Palatal surface and upper molars of Phascolomys Mitchelli. 
