192 
PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF ATISTEALIA. 
2, q) Wombats. The extent of the molar series and the sizes of the individual teeth 
accord, save in the narrower character of the lower molars, with the teeth of the upper 
jaw in the subject of figure 5, Plate XVII. If these fossils are maxillary and mandibular 
specimens of the same species of Wombat, the lower molars are relatively narrower trans- 
versely, compared to the upper ones, than in any of the existing species. 
In the mandibular specimen under consideration we see combinations of characters 
confined severally to distinct species in existing Wombats. I am disposed therefore, 
and for reasons above assigned, to refer this mandibular fossil, with the maxillary one 
above cited, to Phascolomys Mitclielli. 
A second similar specimen of left ramus, including part of the symphysis and of the 
ascending ramus, has a molar series 2 inches in extent, and, as in fig. 5, Plate XIX., the 
teeth have the general characters of those in Phascolomys latifrons ; they are trans- 
versely narrower than in Phascolomys vombatus or Phase, platyrhinus. The ectocrota- 
phyte depression is deeper than in the perforate mandible of that species ; the perfora- 
tion (pi) here shows a similar position and size. The depth of this fossil jaw at the back 
part of the symphysis is 1 inch 5 lines. The symphysis terminates below the interval, 
between the second ( d 4 ) and third (m i) molars. The ectalveolar groove is wider than 
in the subject of fig. 3, Plate XIX., but is deeper than in the Platyrhine and Tasmanian 
Wombats. The symphysis is not bilobed behind, as in fig. 6, Plate XXI. ; but this and 
the before-mentioned differences from that subject probably exemplify the range and seat 
of variety in the mandibular characters of one and the same species. 
The characters noted in the subjects of figs. 4 & 5, Plate XXIII., of fig. 4, Plate 
XXI., and of figs. 2 & 3, Plate XX., are of specific value; but, as in the maxillary 
fossils (Plate XVII. figs. 1 & 2), I do not feel grounds for indicating, after comparison of 
the mandibular fossils from the W ellington-Y alley breccia-caves, more than two species 
of a size not exceeding the known existing Wombats, and not referable thereto. 
§ 15, Mandibular characters of Phascolomys Thomsoni, Ow . — From the freshwater 
deposits of Queensland I have received mandibular fossils of the genus Phascolomys , 
which, with decrease of size, show characters not in accordance with those of any of the 
cave fossils. 
The subject of figs. 8 & 9, Plate XVIII., and fig. 7, Plate XXI., is a right mandibular 
ramus, with slight mutilation at both ends. In the lower contour of the jaw, the depth of 
the ectocrotaphyte depression (/), the breadth of the ectalveolar groove (u), the position 
and size of the intercommunicating foramen (p), the shape of the anterior molar (d 3), 
and the shape and proportions of the incisor (i), so far as these are indicated, the present 
fossil agrees with Phascolomys platyrhinus , and differs from Phascolomys latifrons and 
Phase. Mitclielli. It agrees, however, with these, and differs from both the bare-nosed 
Wombats, in the relative position of the back part of the symphysis (Plate XXI. fig. 7, s ), 
which does not extend beyond the vertical line dropped from the front lobe of mi. 
The grinding-surface of d 3 (Plate XVIII. fig. 9) is an ellipse with the long axis nearly 
parallel with that of the mandible. The outer side of the incisor is transversely convex, 
