BY C. W. DE VIS, M.A. / 



being about the same as in Phalang'ista, that is, considerably less 

 than it is in Si/psipri/mnodon ; it has the same number of ridges 

 (six) as in the latter genus, but these are low, far apai't, irregular 

 in length and direction, and almost confined to the upper half of 

 the tooth ; intermediate, in short, between those of Hijpsiprymno- 

 don, and the ridges not infrequently developed in the premolar of 

 P. vulpina. The crest of the tooth is highest anteriorly (Phalaa- 

 yista), where the penultimate ri Ige on either side meets its fellow 

 in a pi'ominent apical point ; its Ijase externally does not descend 

 below those of the molars (Phalanr/ista). The molars form a 

 straight series of nearly equal breadth [Hijpslprymnodon). A 

 close examination of the three posterior molars in Hypsip)rymnus, 

 H ypsiprymnodon, and Phalanyista, leaves a strong impression that 

 the Musk Rat is, in this part of its dentition, more nearly allied to 

 the Phalangers (as it is by its first molar and by its hind thumb) 

 than to the Kangaroo Rats. It is difficult to translate this 

 impression into words, but it might be said by way of essay that, 

 in the Phalangers the ridge or cusp of the fore lobe on the inner 

 side is central and directly transverse, and the whole lobe very 

 similar to the hinder one, and consetjuently the four parts into 

 which the tooth is divided by the longitudinal sulcus and mesial 

 valley are more regular in size and shape than in the Hysijjrym- 

 nidie, which in the more undulated pattern of the nnolar surface 

 approach the Macropodidaj. In this respect the fossil agrees with 

 H ypsiprymnodoriy but its molars have prebasal talons wanting in 

 the Musk Rat, and these are phalangistine rather than hypsi- 

 pryranine in character. Each is crossed by a strong obliqucj link 

 descending forwards from the outer end of the outer cusp, and bo- 

 coming confluent with the inner moiety of the raised margin of the 

 talon; the outer part of this rim, curving backwards upon the lobe, 

 circumscribes a pit-like depression on that angle of the tooth in 

 the three anterior molars, but, as in Pludangisla, not in the last 

 molar. The hinder lobe of this molar is not much smaller than 

 its fore loVie. Tlie Ineadth of the molar series taken at tlio fore 

 lobe of m^ is four times and one third in its length {llypsiprymnxKs). 

 The fore lobe of the first molar (m') is scarcely differentiated from 



