538 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
young Dlprotodon (Plate XL. figs. 12, 16), the unworn summit of the hind lobe is irre- 
gularly and minutely wrinkled, not divided into small mammilloid tubercles as in the 
Dinothere. In the largest existing species of Kangaroo ( Macropus major and M. lani- 
ger, e. g.) the lower molars have no posterior basal ridge. It is interesting to find that 
this is present in a still larger extinct species ( Macropus atlas , Ow., fig. 14, g ), but it is 
narrower than the anterior basal ridge. In the lower molars of Dlprotodon the posterior 
basal ridge is not only constant, but is broader than the anterior one. 
The sum of the characters of the teeth of Dlprotodon, and the observed varieties and 
modifications due to sex, age, and other conditions, have been given in detail and fully 
illustrated. The most common evidences of extinct Mammals are detached teeth; and 
it seemed desirable to afford sufficient and satisfactory means of determining those of 
the genus Dlprotodon , as thereby the knowledge of its geographical distribution in 
the Australian Continent at the period of its existence may be the more speedily 
acquired. 
A retrospect of the dentition exhibited in the series of specimens above described and 
illustrated brings to view a combination of characters now shown apart in the marsupial 
herbivorous genera Macropus and Phascolomys ; but the Macropode characters prevail 
in number and importance. The small upper incisors (i 2 and i 3) with definable crown 
and fang and concomitant limitation of growth, the same genetic character of the molars 
with the bilophodont type of their crown, testify to the closer affinity of Dlprotodon to 
Macropus. The large, scalpriform, ever-growing first pair of incisors of the upper jaw, 
with the shape, structure, and corresponding genetic character of the lower pair of incisors, 
are resemblances to the Wombat’s dentition; and the same affinity is exemplified in the 
number of the molar teeth. 
In the Macropode group, although not more than five grinders are ever in place in 
one alveolar series of either jaw, seven may be developed. Of these teeth two have no 
homologues calcified in either Phascolomys or Dlprotodon ; these are the small anterior 
teeth symbolized in my 4 Anatomy of Vertebrates’ (vol. iii. p. 380, fig. 296) as d 2 and 
p 3 (Cut, fig. 4). It may be objected that, for certainty on this point, one ought to 
have specimens of jaws of Dlprotodon of an earlier age than that represented in Plates 
XLI. & XLII. My experience in marsupial dentition begets confidence, however, 
that, had a true “ replacing tooth ” been developed in Dlprotodon as in Macropus, its 
crown-germ would have been detected beneath the tooth marked d 3, in the subject of 
the above-cited Plates. 1 also believe that, had a d 2 ever been calcified and in use, as 
in the Kangaroos and Potoroons, some trace of its alveolus would have remained, in 
this young jaw, instead of the continuous, even subtrenchant margin which the diastema 
of the subject of Plate XLI. presents between d 3 and i. 
Since the Wombats in their molar dentition offer precisely the same differences as to 
number and succession of grinders which Dlprotodon presents, we may have the less 
reserve in accepting the evidences of the further resemblance which the molar series adds 
to the incisive one. The extension of the genetic character of the scalpriform incisors 
