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PEOFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
inner side to emerge at the anterior dental outlet ( v ) ; the “ mylo-hyoid groove ” is 
broader and less deep than in Plate XXXVI. fig. 2, w. The characters of the ectalveoiar 
groove, of the postal veolar ridge, and of the ectocrotaphyte fossa (f) agree with those of 
the type mandible of Phascolomys gigas. 
The present specimen was discovered by M. Satche St. Jean, at St. Jean Station, 
Queensland, in the bed of a tributary creek of the Condamine River. 
The last specimen which I have now to notice was obtained by F. Nicholson, Esq. ? 
from the same freshwater deposits at Clifton Plains, Darling Downs, Queensland. I am 
indebted to the kindness of Professor Hakkness, of Queen’s College, Cork, for the oppor- 
tunity of here describing and figuring it. It either exemplifies the largest observed 
variety of Phascolomys gigas , or indicates a still larger species, i. e. one in which modifi- 
cations of the shape of the jaw may be associated with its superiority of size. Of this 
the mutilated state of the fragment does not permit me to judge, and I am disposed to 
refer the specimen to a large old male of Phascolomys gigas. 
The longitudinal extent of the outlets of the last three molars of Mr. Nicholson’s fossil 
(Plate XXXVIII. fig. 4, m 1,2,3) is 3 inches 1 line ; they show the same kind and degree 
of decrease of size from the first to the third as in the smaller examples of the species. 
The breadth and apparent depth of the ectalveoiar groove (ib. figs. 3 & 4, u) are as in 
the first-described mandible (Plates XXXVI. & XXXVII.). The fore part of the base 
of the coronoid or ascending ramus (ib. fig. 3, q) and of the ectocrotaphyte ridge 
(ib. h) show likewise the same relative positions. On the inner fractured side of this 
specimen the large inner division of the dental canal is seen about 9 lines above the closed 
ends of the last two alveoli. 
§ 4. Conclusion . — In the case of Phascolomys , as of most Mammalian genera, when 
due time and pains are applied to the acquisition and study of the fossil evidences, the 
number of species which have passed away is found to exceed that of the living ones 
which remain. 
Until comparatively lately the Wombat was known to zoologists as a solitary excep- 
tional form of small Tasmanian marsupial, peculiar in its scalpriform dentition combined 
with burrowing habits*. We now know this generic form under many specific structural 
modifications, and with gradations of bulk rising from that of a Marmot to that of a Tapir. 
The rodent type of incisors, both as to number and kind, are retained in all, certainly 
in the lower jaw of the gigantic species; but it would not be safe to infer that the 
subjects of the present Paper burrowed like the smaller living Wombats. 
If we knew the Plare (Lcqms timidus ) only by fossil remains, we should err in attri- 
buting to it the habits and mode of life of the smaller species, Lejgns cuniculus. It is 
probable that the larger extinct Wombats did not conceal themselves under ground. 
What we know is, that of the series of forms specifically varying the generic type of 
Phascolomys the larger ones have perished. Here, as in the case of the gigantic 
wingless birds of New Zealand, size and bulk seem to have been a disadvantage in the 
* Hence the synonym, Phascolomys fossor, of "Wagner. 
