309 



two transverse eminences, the summits of which had just begun to be 

 abraded by mastication before the animal perished, is better displayed than 

 in No. 1449 : they are more compressed than in the Tapir and Dinothere, 

 and their lamelliform summits rise higher beyond their basal connections 

 than in the Kangaroo : the median connecting ridge which extends 

 between the two transverse eminences longitudinally or in the axis of the 

 jaw, in the molars of the Kangaroo, is very feebly indicated in the Di- 

 protodon : the anteriorly concave curve of the summits of the transverse 

 ridges is more regular and equable and greater than in the tapiroid Pachy- 

 derms, the Dinothere, or the Kangaroo. The two fangs, the contiguous 

 surfaces of which present the deep and wide longitudinal 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. 



From the alluvial or newer tertiary deposits in the district of Mel- 

 bourne, Australia. Presented by Dr. Hobson. 



1493. The second molar tooth, left side, lower jaw, of the Diprotodon australis, 

 from an older individual than the preceding. The anterior 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 demon- 

 strates, what is obscurely indicated in No. 1460, that besides the two prin- 

 cipal eminences there is a small anterior basal ridge and a thick obtuse 

 posterior ridge ascending 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 emi- 

 nence ; 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 interspace ; indi- 

 cating, 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 punctate surface as 

 in the molars Nos. 1469 and 1487, that character being more conspi- 



