PEOFESSOR OWEX ON THE FOSSIL MAMMALS OF AUSTRALIA. 



249 



XXXYI. iig. 3) cannot have worked, in the same head, upon an upper series of only 

 3 inches G lines (Plate XXXV, figs. 1 & 3). The anterior molar of the lower or movable 

 jaw in Pliascolomys medius (Plate XXXIV. fig. 2, d 3) has a somewhat smaller extent of 

 grinding-surface, as in all existing AVombats, than the corresponding tooth of the upper 

 or fixed jaw (Plate XXXII. fig. 2, d 3, and Plate XXXIII. fig. 2, d 3). The smallest 

 example of 3 in the remains of large Wombats yet to be described gives 9 lines and 

 4^ lines as the two diameters of its almost elliptical grinding-surface (Plates XXXVI. 

 & XXXVII. d 3). Such a tooth cannot have belonged to the same species as the one 

 which has an upper anterior molar with the dimensions above given as characteristic of 

 Fhascolomys magnus (Plate XXXV. d 3). 



Of this species the lower jaw and teeth have not yet come under my observation. All 

 the examples of the large extinct Wombats now before me for description belong to 

 the species Fhascolomys gif/as, of which the grinding-surface of a lower molar is figured 

 in the " Article " quoted above, and in my 'Palaeontology' (p. 431, fig. 172, 2nd ed. 18G1); 

 the former existence of which Wombat I noticed, some years before, in my second 

 memoir " On the Osteology of the Marsupialia" *. 



Satisfactory evidence of this species has since reached me, of which I propose, first, to 

 describe a considerable proportion of the mandible, obtained by Edw^ard S. Hill, Esq., 

 from a freshwater deposit at Eton Vale, Darling Downs, in 1863, and presented by 

 Sir Daniel Coopee, Bart., to the British Museum. 



It consists of the right ramus (Plate XXXVI. fig. 1) with the fore part broken off 

 near the socket of the first molar (d 3), and with some mutilation of the outstanding 

 parts of the ascending ramus ; also of the fore part of the left ramus (ib. fig. 2), with 

 the hind part broken off at the socket of the penultimate molar (m 2). They are both 

 parts of the same mandible, and I have therefore supplied, in the subjects of Plate 

 XXXVI. fig. 2, Plate XXXVII. fig. 1, and Plate XXXVIII. fig. 1, from one ramus 

 what was wanting in the other. 



Eeference to Plate xxii. Phil. Trans. 1872, where the side view is given of the mandible 

 in the three known living species of Fhascolomys, will make at once appreciable the 

 character of the present extinct Wombat, in the minor relative antero-posterior extent 

 of the ascending ramus, and its greater relative height before dividing into the condylar 

 (b) and coronoid (c) processes. The intervening notch sinks nearly to the level of the 

 grinding-surface of the molars in the recent and smaller extinct Wombats ; whereas in 

 Fhascolomys gigas the common plate (f,g) rises much higher before dividing into b and c 

 (Plate XXXVI. figs. 1 & 2). The fore-and-aft extent of the rising branch at the neck 

 of the condyle equals in extent that of the last four molars in Fhascolomys jjlatyi'himis^ 



* Trans. Zool. Soc. vol. iii. p. 30G, 1S45 : — " I have recently obtained evidence from the postpliocene deposits 

 of the district of Melbourne, through the kindness of my friend Dr. Hobsox, of an extinct Wombat, or true 

 Fhascolomys, at least four times as large as either of the known existing species." These were Pliascolomys 

 vomhatus and Pliascolomys latifvons; the somewhat larger continental Wombat {Pliascolomys pJatyrMnus) had 

 not then been determined. 



MDCCCLXXII. 2 L 



