PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
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type of Sthenurus ( Macropus ) Atlas (comp. fig. 18,^3 with fig. 4, p 3, Plate XXII.). 
But I had not at that time the further satisfaction of determining the characters of the 
maxillary dentition of Macropus Titan by fossils of that species, either at the corre- 
sponding immature stage of the animal affording the mandibular fragment or of full- 
grown individuals. I have subsequently received both desiderata, some of which 
reached me in time to notice in the under-cited work*, and of which figures are now 
for the first time given. The maxillary specimen (Plate XXI. figs. 6-9), in its phase 
of dentition, relates as closely to the mandibular one (Plate XXII. figs. 17, 18) as does 
the upper jaw of Sthenurus Atlas (Plate XXIV. figs. 4 & 5) to the portion of lower 
jaw (Plate XXII. figs. 3 & 4). 
The fossil in question (Plate XXI. figs. 6-9) is not from the Breccia-cave of Welling- 
ton Valley, but from a freshwater’ bed or drift in Queensland, where it was obtained and 
transmitted to me by my friend George Bennett, M.D., F.L.S. This is interesting as 
evidence of the range of the large and now extinct species. It shows the usual state 
of petrifaction of fossils from that formation and locality. It is a portion of the left 
maxillary bone, with a series of five molars in situ. The first (ib. ib. d 2 ), slightly muti- 
lated externally, has a simple subcompressed unilobate (or subbilobate V) crown, broadest 
behind, of much smaller size than that of the following two-ridged grinder ( d 3) ; its 
working-surface had been worn so as to expose a broad field of dentine. The next 
tooth ( d 3) shows a minor degree of abrasion, the third molar (d 4) still less. In the 
fourth (to 1 ) the summits of the two transverse ridges have just been touched ; those of 
the hindmost molar (to 2) in place had not come into use, although they attained nearly 
the level of the ridges of the antecedent tooth. Moreover, behind the fifth molar was 
the fore part of a smooth subspherical cavity (ib. fig. 9), plainly the formative alveolus of 
another molar (to 3) still to come into place. 
Accordingly the five molar teeth in this maxillary fossil I interpreted as homotypal 
in the upper jaw with the five molars in the lower jaw of a similarly immature Macro- 
pus major. Adopting the symbols in fig. 296, d, vol. iii. of my ‘ Anatomy of Verte- 
brates,’ those of the five teeth in the present fossil would be : — d 2, d 3, d 4, m 1 , & to 2. 
To test this conclusion I proceeded to remove the outer table of the jaw-bone above d 3, 
and detected the germ of p 3 (ib. fig. 6), in a stage of development like that of p 3 in 
the lower jaw of the type specimen (Plate XXII. fig. 18), and corresponding with the 
state of the dentition in the upper jaw of Macropus erubescens (Plate XX. fig. 6). The 
back tooth, when formed in the hindmost closed alveolus, would be to 3, completing the 
total of seven teeth developed in the molar series of the Macropodidae. 
In the upper premolar of Macropus Titan the crown consists of two simple, conical, 
subcompressed lobes, the hindmost being thickest posteriorly ; it is supported on two 
roots, the formation of which had commenced in the specimen described : its movement 
into place, or into the masticatory series, would have involved the shedding of d 2 and 
* Catalogue of the Fossil Mammalia and Birds in the Museum of the Royal College of Surgeons, 4to, 
1845, p. 324, Nos. 1500 and 1510. 
