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figs. 1, 2, 3) this ridge (h) begins near the lower border of the ramus ; in the fossil 

 (ib. fig. 6, h) it begins midway between the lower and upper borders, and on a vertical 

 parallel with the third or antepenultimate molar (m i) — consequently more in advance 

 than in the recent Wombats, in which both the ridge and the base of the coronoid (q) begin 

 below the fore part of the penultimate molar (ra 2). Both penultimate and last molars 

 are in place and are worn in the fossil, so the differences above noted cannot relate to 

 nonage. The beginning of the ectocrotaphyte ridge is 10^ lines below the outlet of the 

 first division of the alveolus of m 2 in Phase, latifrons (ib. fig. 3, h), and is 1 inch below the 

 same part in Phase, platyrhinus (ib. fig. 2, h) ; in the fossil it is 6 lines below the hind 

 division of the alveolus of mi. 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 LII. 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, Jc) than in Phase, platy- 

 rhinus (ib. fig. 2, Jc). 



The ectalveolar groove is longer, deeper, and narrower in the fossil (Plate LIII. 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 LVI. 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 LIII. fig. 3, m 2, m 3) are narrower than 

 those in Phase, latifrons (Plate LIV. fig. 1, m 2, m 3), as are the anterior molars in the 

 fossil previously described (ib. fig. 2, d 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 



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