190 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
division of the alveolus of m 1 . The anterior origin of the coronoid appears to be pro- 
portionally advanced in the fossil. The outer surface of the ramus below the beginning 
of the ectocrotaphyte ridge slopes more gradually inward and lower down before passing 
into the broad under surface of the jaw in the fossil (Plate XXII. fig. 6). In the 
recent Wombats the same surface curves, with a stronger and shorter convexity, into the 
lower border, yet less abruptly in Phase, latifrons (ib. fig. 3, k) than in Phase, fflaty- 
rhinus (ib. fig. 2, k). 
The ectalveolar groove is longer, deeper, and narrower in the fossil (Plate XIX. fig. 3, u), 
owing to the more advanced origin of the coronoid (q) and its greater proximity to the 
last two alveoli (m 2, m 3 ) ; this differential character is still more marked as compared 
with the Platyrhine species (ib. fig. 2 , u). From so much of the entocrotaphyte ridge, 
or anterior beginning of the inflected angle, as is preserved, the degree of inflection 
appears to have been less in this fossil (Plate XXIII. fig. 5, a) than in the recent species 
(ib. figs. 1, 2 , 3, a). The surface broadening as it recedes, between the ecto- and ento- 
crotaphyte ridges, is not only flattened but becomes rather concave in the fossil toward 
the inner border. 
The two hindmost molars in place (Plate XIX. fig. 3, m 2, m 3) are narrower than 
those in Phase, latifrons (Plate XX. fig. 1, m 2, m 3), as are the anterior molars in the 
fossil previously described (ib. fig. 2 , cl 3, d 4). To the species represented by the last- 
cited fossil, I am disposed, from the resemblance of the symphysis to that in the imper- 
forate variety of Phase, latifrons, to refer the present fossil. They might be parts of the 
same mandible, as well as of the same species ; but more complete specimens must con- 
firm or confute this supposition. It is certain that both fossils show the nearest resem- 
blance to the mandibular imperforate variety of Phascolomys latifrons above named, 
yet with marked differences, in value equalling those interpreted and accepted as 
specific. The part of the dental canal which courses along the inner side of the molar 
alveoli and the bottoms of the last two alveoli are exposed by fracture of the thin film 
of bone originally covering them. 
In reference to the characters of the two portions of fossil mandible above defined, as 
they plainly justify the inference that they belonged to a species of Phascolomys as 
distinct from the three accepted recent species as these differ from one another, each 
might be indicated by a specific name ; and it may ultimately prove that they do belong 
to distinct species. 
The same remark applies to both or either in relation to the maxillary fossil from 
the same cavern (Plate XVII. figs. 2 & 6) which I have referred to a Phascolomys 
Krefftii. 
Considering, however, that the two portions of mandibles combine, like that maxillary 
one, characters of affinity to Phascolomys latifrons with differential ones forbidding a 
reference to that species, it may be, and may be probable even, that they all belong to 
the same extinct species. I prefer, therefore, to indicate them as parts of a Phascolomys 
Krefftii, and leave to those who may be so fortunate as to obtain evidence to the con- 
