349 



The first molar (Plate LXI. figs. 1 & 3, d 3) is subbilobed, through opposite longitudinal 

 shallow grooves equally dividing the tooth. The tendency to a gain of grinding-surface 

 in the direction of the jaw's axis seen in the same tooth of Phascolomys medius is in the 

 larger species carried further, so as to substitute for the representative of one half or 

 lobe of the succeeding molars in the anterior one of smaller Wombats a more simplified 

 condition of the normal bilobed phascolomydian type of molar. The enamel of d 3 in 

 Phascolomys gigas is continued from the outer over the front side, and along nearly the 

 whole of the hind side of the tooth. A coat of cement of similar thickness covers the 

 inner side, and is continued more thinly upon the enamel. The surface of the enamel 

 is longitudinally rugoso-striate. 



All the succeeding molars have a partial coat of enamel, extending from the outer 

 side upon the fore part to where this comes into contact with the antecedent tooth, and 

 continued, perhaps, a little further upon the hind surface. The rest of the dentine has 

 the coating of cement. The proportions of the several teeth are shown in the figures 

 above cited. 



As before remarked, the smaller size of the last molar indicates the Latifront Wombat 

 to be nearer akin to the extinct giant than are the bare-nosed living species. The 

 same affinity is shown by the small size of the lower incisors in Phascolomys gigas 

 (Plate LXV. figs. 1, i, 2, 3, 4). They are smaller, especially narrower, in Phascolomys 

 latifrons than in Phase, platyrhinus and Phase, vombatus, and are, relatively, still 

 smaller in Phase, gigas, with a distinctive shape. But the characters of the lower pair 

 of incisors are better shown in another mandibular specimen of the present large species. 



The section or transverse fracture of the hollow base of the right incisor is shown in 

 Plate LXII. fig. 2, i ; the length and curvature of the implanted part of the second 

 molar (d *) are seen in the same figure, in which e e indicates the anterior terminal line 

 of the outer enamel. The hinder fracture of the left ramus of the same jaw (ib. fig. 3) 

 shows the length and curve of the penultimate molar (to 2), and the posterior terminal 

 line of its partial covering of enamel (e). 



Of the above-described instructive specimen of Phascolomys gigas little more than an 

 inch of the diastemal part of the jaw is preserved (Plate LXI. figs. 1 & 2, /). Fortu- 

 nately, the first specimen which made known to me the fact of so large a Wombat having 

 formerly existed in Australia included 2 inches 8 lines of the diastemal part of the jaw, 

 which contracts rapidly to the terminal outlets of the incisive alveoli (Plate LXIV. 

 figs. 1 & 2) ; whence I conclude that but little had been broken away from that end of 

 the mandible. 



The subject of Plate LXIV. figs. 1,2, 3 was obtained from "a salt-lake, nearly 100 

 miles west of Melbourne," and was transmitted to me by Dr. Hobson*. It is the sym- 

 physial end of the mandible, with 4^ inches of the joint (s, s'), the obliteration of which 

 indicates the age of the individual ; it includes the implanted parts of the incisors (i 1 ), 

 and of the three anterior molars of each ramus (fig. ] ). The under part of the symphysis 



*• Letter from Dr. Hobson, March 3rd, 1844. 



33* 



