343 



part of the ectocrotaphyte depression (f), bounded below by the prominent outstanding 

 ridge (h!, h, fig. 1), is less deep than in the bare-nosed Wombats, and is more gradually 

 excavated, as in the hairy-nosed species. 



The ramus maintains its depth (1 inch 10 lines) to the socket of the first molar (Plate 

 LIX. d 3, figs. 1 & 2). The hind part of the symphysis (ib. fig. 3, s) is on the vertical 

 parallel of the hind part of the second molar (fig. 2, d, 4), being rather more advanced than 

 in Phascolomys latifrons (Plate LV. fig. 3, s), and much more so than in Phase. jplatyrhinus 

 (ib. fig. 2, s) or Phase, vombatus (ib. fig. 1, s). The upper surface of the symphysis 

 (Plate LIX. fig. 3, s) repeats the character of the opposed palatal part of the upper jaw 

 (Plate LVII. & LVIII. 21', 22') in its degree of transverse concavity; and this, at the dia- 

 stemal tract, is bounded by lateral ridges, sharper than those above ; they indicate a 

 slightly curved course as they advance, concave outward, so far as they extend in the 

 fossil. These characters of the upper surface of the symphysis are most nearly repeated 

 by Phascolomys Krefftii (Plate LIV. fig. 2, I, s) amongst the smaller Wombats ; but in 

 that extinct species the symphysis extends back as far as it does in Phase, platyrhinus 

 or Phase, vombatus (Plate LITI. figs. 1 & 2). In Phase, latifrons the symphysis is shorter, 

 more concave and more definitely bounded above than in the bare-nosed Wombats, but 

 is not so much so as in Phascolomys Krefftii. The lower contour of the symphysis in 

 Phascolomys medius rises at a less open angle with the axis of the ramus than in Phase, 

 latifrons, and still less so than in the bare-nosed species. The lower surface shows the 

 pair of vascular outlets, of small size, 15 lines in advance of the hind border. The 

 anterior outlet of the dental canal (Plate LIX. fig. 1, v) is relatively rather nearer the 

 socket of d 3 than in the smaller fossil and recent Wombats. The vertical convexity of 

 the outer wall of the ramus and comparative flatness of the postsymphysial inner wall 

 are according to the generic type, and relate to the direction of convexity of the long, 

 bent, deeply implanted, ever-growing molars. 



The first molar (d 3, ib. figs. 1, 2, 3) has the usual generic small size and simple form, 

 representing, as it were, like its homotype above, one half of the succeeding molars. 

 The grinding-surface resembles that of the upper jaw in being suboval, with the long 

 axis lengthwise. In this it differs from Phascolomys latifrons, Phase. MitchelU, and 

 Phase. Krefftii, in which that surface is subquadrate, and it resembles, rather, Phasco- 

 lomys platyrhinus ; but the larger end of the oval is at the fore part of the tooth in 

 Phase, medius, not at the hind part, as is usually seen in Phase, platyrhinus. The 

 fore part of d % in Phase, medius shows a feeble longitudinal groove, as in Phase, lati- 

 frons. The enamel, as usual, coats the outer and fore part of the tooth, but is not 

 extended so far from the fore part upon the inner side as in Phase, latifrons. There 

 seems to be a slight interruption in the course of the enamel at the middle of the fore 

 part of the tooth, which I have noticed in some of the smaller Wombats. The enamel 

 was coated by cement in the fossil. 



The succeeding molars slightly decrease in breadth of grinding-surface from the third 

 (Plate LIX. m 1), the decrease being most marked in the hind lobe of the last molar. This 



