PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
251 
shows each transverse lobe worn to near its base, exposing corresponding broad 
tracts of dentine united by a linear strip along the base of the mid link. In m 1 
the dentine exposed on the transverse lobes is a linear tract, rather broader on the front 
lobe ; the front (s) and mid (r) links show abrasion, but not carried to the exposure of 
the dentine. In m 2 the enamelled summits of the ridges are slightly abraded ; m 3 , as 
before stated, had not risen into place. 
The molar characteristics of the species ( Macropus Titan) are well exemplified in this 
cave-specimen. Sufficient of the palate is preserved to show, as in the preceding one, 
that it had no large vacuities. The relative position of the zygomatic pier ( 21 ) 
seems to have retrograded as compared with fig. 8 ; but it still strengthens the jaw 
where the hindmost molar here (m 2) was in use ; when m 3 comes into place and takes 
its share, the jaw, as we shall see again, becomes concomitantly modified. 
The specimen described and figured formed part of the collection of duplicate fossils 
obtained, under the favourable circumstances detailed in the Philosophical Transactions 
for 1870, p. 569, by Professor Thomson and Mr. Krefft from the Breccia-cavern dis- 
covered by Sir Thomas L. Mitchell, C.B. 
In a collection of marsupial fossils at Worcester I recognized a portion of the right 
upper jaw, with the molar series, of a Macropus Titan exemplifying the stage of dentition 
when the last molar as well as the premolar had come into place, but the former so 
recently that the zygomatic pier had not much receded in position. The first and 
second deciduous molars ( d 2 and d 3) had been shed. The part of the series d 4 to m 2 
inclusive occupied a space rather short of that containing the homologous teeth in the 
younger specimen (Plate XXI. fig. 10) ; but the structure of the last two teeth and the 
proportions of the premolar were those of Macropus Titan. Unfortunately the crowns 
of the first three teeth had suffered fracture. A portion of the hinder fold of enamel 
remained on the broken base of the crown of the premolar, showing that the hind lobe 
of that tooth, besides being thicker than the fore one, was divided into an outer and 
inner lobule. Its longitudinal extent agreed with the crown of the germ oi p 3 exposed 
in the subject of fig. 6, Plate XXI. 
The same phase of dentition is exemplified in a similar portion of the right maxillary of 
another and somewhat larger individual of Macropus Titan (Plate XXI. fig. 11), in which 
the crown of the premolar is entire, and shows by its unworn condition that it had but 
recently risen into place. This tooth instructively contrasts with the next grinder, 
which is worn down so as to expose a continuous field of dentine, encroached upon by 
two opposite folds of enamel from the inner and outer sides of the crown meeting at 
the middle. In the next tooth the dentine is exposed upon each of the transverse 
lobes and upon part of the anterior “ link.” In the penultimate molar a thin line of 
dentine appears on the front lobe, but the enamel is not worn down so far in the hind 
lobe. The enamel ridge of the front lobe of the last molar is touched by abrasion. The 
crown of the premolar shows it to have been the last of the series of five teeth now come 
into place. It is trilobed : externally it shows only the bilobed structure (as in fig. 6) ; 
