PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
255 
The crowns of the upper molars are, as usual, broader than those of the lower jaw, 
and, as in MacYopus major and Nototherium , the last lower molar has a greater longi- 
tudinal extent of grinding-surface than the tooth above. 
In another specimen of a smaller portion of the left maxillary of Macropus Titan in 
the University Museum of Geology, Oxford, the dentition is shown at the same phase 
of development as in the preceding fossil, with a rather greater degree of abrasion. A 
thin line of dentine is exposed upon the summit of the anterior lobe of m3; the mid 
link is worn to its base, exposing a linear tract of dentine uniting the broader field upon 
the anterior and posterior lobes. The size and other characters of the upper molars in 
figs. 10-14 (Plate XXII.) are satisfactorily repeated in the present evidence of Macropus 
Titan. 
Both specimens are from the freshwater beds or drifts of Queensland, and were pre- 
sented to the Oxford Museum by Sir Charles Nicholson, Bart., M.D., and formerly 
Speaker of the Legislative Assembly at Sydney, New South Wales. 
The portiou of right upper maxillary (Plate XXIII. figs. 2 & 3) in which the adult 
series of five grinders had been acquired, but with posthumous mutilation of the crowns 
of the two anterior ones, shows a modification of those of the three following ( m 1, m 2, 
m 3) which I now know to be a variety, although not such as to induce me to refer the 
fossil to another species. The mid link (fig. 3, r) as it passes forward from the hind to 
the front lobe expands and divides ; the more direct or normal continuation, after reaching 
the front lobe, bends to terminate or be continued into the inner border of that lobe ; 
the other lower and shorter division turns outward to be lost upon the lower part of 
the outer half of the hind surface of the front lobe. 
This character I briefly expressed as “ a more complex form of the longitudinal ridge 
connecting the two principal transverse eminences ” than in Macropus major or Macro- 
pus laniger , in my ‘Catalogue of the Fossil Mammals* in the Museum of the Royal 
College of Surgeons ’ ; at the date of which work this specimen was the sole evidence of 
the upper jaw and teeth which appeared to me to be referrible to Macropus Titan. 
Besides the structure of the grinding- surface of the molars above defined, those in 
fig. 3, Plate XXIII., are arranged with a curve rather more marked than in the subject 
of fig. 11, Plate XXII. ; but as the teeth here are less straight than those in the 
subject of fig. 8, Plate XXI., this seems to be but a ground of variety. The relative 
position of the zygomatic pier in figs. 2 & 3, Plate XXIII., may relate to the recent 
movement of m 3 into its working position : the untouched lobes of this tooth are longer 
and sharper than usual ; yet the general concordance with the molar characteristics 
of Macropus Titan lead me still to refer the specimen No. 1510 to that species. 
The modification of the mid link seems a small matter, but is not so in the actual 
phase of zoology. Evolutionally speaking, this variety may be viewed as either a rem- 
nant or a dawn of a complex condition of the part which will be described in 
subjects of a subsequent section. 
* 4to, 1845, p. 324, No. 1510. 
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