PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
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XXXVI. lig. 3) cannot have worked, in the same head, upon an upper series of only 
3 inches 6 lines (Plate XXXV. figs. 1 & 3). The anterior molar of the lower or movable 
jaw in Phascolomys medius (Plate XXXIV. fig. 2 , d 3) has a somewhat smaller extent of 
grinding-surface, as in all existing Wombats, 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 d 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 
Phascolomys 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 Phascolomys gigas , 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. 1861); 
the former existence of which Wombat I noticed, some years before, in my second 
memoir “ O 11 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 Edward S. Hill, Esq., 
from a freshwater deposit at Eton Vale, Darling Downs, in 1863, and presented by 
Sir Daniel Cooper, 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. 
Deference to Plate xxii. Phil. Trans. 1872, where the side view is given of the mandible 
in the three known living species of Phascolomys, 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 
Phascolomys 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 Phascolomys jglatyrhinns, 
* Trans. Zool. Soc. vol. iii. p. 306, 1845 : — “ I have recently obtained evidence from the postpliocene deposits 
of the district of Melbourne, through the kindness of ray frieud Dr. Hobson, of an extinct Wombat, or true 
Phascolomys, at least four times as large as either of the known existing species.” These were Phascolomys 
vombatus and Phascolomys latifrons ; the somewhat larger continental Wombat {Phascolomys pi atyrhinus) had 
not then been determined. 
2 L 
MDCCCLXXII. 
