FOSSIL MAMMALS. 281 



laches. 

 Length of crown ----- 4 

 Breadth at anterior ridge - - - 2 j^g 



Breadth of posterior ridge - - - 2|-J 

 Length of roots ----- 4 

 The crown is surmounted by three ridges, and is terminated at either end by a rudimentary 

 one. The three principal ones are much worn, and give the usual characteristic trefoil-shaped 

 sections ; the right and left halves of each ridge are separated by a deep cleft, and the portions 

 of enamel on either side of this are very distinctly crenulated, but those of the outer half much 

 the most so. The outer section is likewise larger than the inner. There is no basal ridge, nor 

 is the side of the crown tuberculated ; the enamel generally is quite smooth, but is somewhat 

 channeled in the interspaces of the inner halves of the ridges ; on the outer border a blunt 

 tubercle is seen between the bases of the -first and second and the second and third ridges. 

 These last are slightly oblique, their direction being outwards and backwards. The two roots 

 which su]3port the crown are about four inches in length, one of them being situated beneath 

 the first ridge and the other beneath the second and the third ; this last, however, is partially 

 subdivided by a deep groove. The great length of the roots corresponds with the attrition of 

 the crown, the former increasing as the latter diminishes in the ordinary use of the teeth. 



This tooth is of the right side, and corresponds with the one marked V (PL xii. Figs. 1, 2) 

 in the lower jaw, from which its dimensions vary but slightly. 



36* 



