ON THE EXTINCT MAMMALS OF AUSTRALIA. 227 



base of the left incisive tusk of the Diprotodon australis ; showing the line 

 where the rugose punctate, as if worm-eaten, enamel ceases at the angle be- 

 tween the under and inner surfaces of the tusk, and the coat of cement cover- 

 ing the unenameled dentine, the smooth pulp-cavity gradually widening to 

 the base of the tusk, is exposed to the extent of three inches. This portion of 

 the great incisor is identical in form and structure with the specimen from 

 the bone-cave of Wellington Valley, figured and described in Sir T. L. Mit- 

 chell's ' Expeditions into Australia,' vol. ii. p, 362, pi. 31, figs. 1 and 2, and 

 with that from the Condamine river above described. 



The next specimen is the crown and beginning of the fangs of the antepe- 

 nultimate molar, right side, lower jaw, of the same Diprotodon australis. The 

 form of the two transA'erse eminences, the summits of which had just begun 

 to be abraded by mastication before the animal perished, is well displayed : 

 they are more compressed than in the Tapir and Dinothere, and their lamelli- 

 form summits rise higher beyond their basal connexions than in the Kan- 

 garoo. The median connecting ridge which extends between the two trans- 

 verse eminences longitudinally or in the axis of the jaw, in the molars of the 

 Kangaroo, is very feebly indicated in the Diprotodon ; the anteriorly concave 

 curve of the summits of the transverse ridges is more regular and equable 

 and greater than in the Tapiroid Pachyderms, the Dinothere or the Kangaroo. 

 The cement, though thin upon the crown, is most conspicuous at the bottom 

 of the valley between the two transverse eminences ; as in the molar tooth 

 of Diprotodon described in the 'Annals of Nat. Hist.' May 1843. The two 

 fangs, the contiguous surfaces of which present the deep and wide longitu- 

 dinal groove, as in the Tapiroid Pachyderms and the Kangaroo, are connected 

 together at their base by a ridge, coated thickly with cement, and extending 

 longitudinally between the beginnings of the opposite grooves. 



The third specimen is the second molar tooth, left side, lower jaw, of the 

 Diprotodon australis, from an older individual than the preceding. The an- 

 terior fang is broken off, the posterior one is preserved to the extent of one 

 inch and a half; the crown of the tooth is entire, except where the summits of 

 the two transverse ridges have been abraded by mastication : it demonstrates 

 what is obscurely indicated in the corresponding molar tooth in the fragment 

 of jaw from the Condamine river, that, besides the two principal eminences, 

 there is a small anterior basal ridge, and a thick obtuse posterior ridge, ascend- 

 ing a little obliquely from the outer to the inner side of the tooth ; from the 

 anterior and posterior extremities of each basal ridge, a lower ridge extends 

 upwards to the summit of the principal eminence ; these eminences are also 

 connected together by a short ridge at the outer and at the inner part of their 

 basal interspace, and each of the principal eminences swells out near the 

 middle of their intei'space, indicating as it were the median longitudinal ridge 

 which connects the two chief transverse eminences in the crown of the molar 

 of the Kangaroo. The enamel presents the same rugose-reticulate and punc- 

 tate surface as in the molars of the specimen from the Condamine, that super- 

 ficial character being more conspicuous in the fore and back part of the 

 coronal eminences than upon their outer and inner sides. The outer border 

 of the transverse eminences is more convex than the inner one. 



The fourth specimen is the third or antepenultimate molar, left side, lower 

 jaw, of the same individual Diprotodon australis. Like the preceding tooth, 

 this gives evidence of an older, and likewise a rather larger individual than 

 the second specimen : the crown has been more worn, and shows better the 

 depth of the interspace between the two principal ridges, the slight production 

 of the middle of the posterior surface of the anterior ridge, and the depres- 

 sion on the opposite surface of the posterior ridge. The antero-posterior ex- 



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