2l)S 



young Diprotodon (Plate XXIV. figs. 12, 1G), the unworn summit of the hind lobe is 

 irregularly 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 Diprotodon the posterior 

 basal ridge is not only constant, but is broader than the anterior one. 



The sum of the characters of the teeth of Diprotodon, 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 Diprotodon, 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 Diprotodon 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 Diprotodon ; these are the small anterior 

 teeth symbolized in my ' 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 Diprotodon of an earlier age than that represented in Plates 

 XXVI. & XXVII. My experience in marsupial dentition begets confidence, however, 

 that, had a true " replacing tooth " been developed in Diprotodon 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 XXVI. 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 Diprotodon 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 



