334 



and size of the intercommunicating foramen (p), the shape of the anterior molar (d 3 ), 

 and the Bhape and proportions of the incisor (t), so far as these are indicated, the present 

 fossil agrees with Phascolomys platyrhinus, and differs from Phascolomys latifrons and 

 Phase. Mitchelli. 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 LV. fig. 7, s), 

 which does not extend beyond the vertical line dropped from the front lobe of m i. 



The grinding-surface of d 3 (Plate LI. 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, 

 and curves uninterruptedly to the underside, as in Phase, platyrhinus and Phase, vom- 

 batus. In size this fossil does not exceed the Tasmanian species. The antero-posterior 

 extent of the working-surfaces of the five molars is the same, viz. 1 inch 11 lines; but 

 the teeth are rather narrower transversely, and the last molar, especially its hinder lobe, 

 shows a greater decrease, as in the Hairy-nosed Wombat. 



I indicate the species of Phascolomys, from which the present fossil has been derived, 

 by the name of a former estimable Professor of Geology in the Sydney University, New 

 South Wales, Alex. M. Thomson, D.Sc. The specimen is from a lacustrine deposit at 

 (xowrie, Darling Downs, Queensland, and was presented to the British Museum by Sir 

 William M c Arthur, Bart. 



§ 16. Mandibular fossil of Phascolomys platyrhinus, Ow. — The subject of figs. 3 & 4, 

 Plate LIV., well exemplifies the differences by which Phascolomys platyrhinus differs 

 from Phascolomys Thomsoni. The symphysis has the same backward extent and relative 

 position to the molar series as in the recent specimen (Plate LIII. fig. 2) ; the character 

 of the upper surface of the diastemal tract (I) is repeated ; the formal characters of d s 

 and of i in the fossil are precisely those in the recent continental bare-nosed Wombat : 

 in size the fossil equals the largest living specimen of that species. The antero-posterior 

 extent of the molar series is 2 inches 1\ lines. The shape and proportions of the molars 

 characteristic of Phascolomys platyrhinus are closely preserved in the fossil. It was 

 obtained from the bed of a tributary of the Condamine River, Queensland, by Edward S. 

 Hill, Esq., and shows that the characters of the actual Platyrhine species were esta- 

 blished at a period coeval with the existence of Diprotodon and Thylacoleo. 



§ 17. Mandibular and lower molary characters of Phascolomys parvus, O10. — With 

 present evidence of the constancy of size of the molar series of teeth in existing and 

 extinct species of Wombat, such series fully in place and well worn, having a longitudinal 

 extent of 1 inch 5 lines, cannot be referred to a species with a longitudinal extent of 

 molars never less than 1 inch 9 lines, and usually more : as, e. g., in the Tasmanian 

 Wombat, which is the smallest of the known existing species. The series of molars in 

 Plate LIII. fig. 6, contrasted with those in fig. 1, is implanted in a mandible of similar 

 small size (Plate LIV. figs. 6 & 7). In the lower contour, the depth of the ectocrota- 

 phyte fossa (f), the breadth of the ectalveolar groove, the shape and size of the incisor, 

 and the shape of the grinding-surface of the anterior molar (d 3) this fossil agrees with 

 Phascolomys platyrhinus. But the symphysis (Plate LIV. fig. 7, 3) does not extend so far 



