INSECTIVORA 



and set in the jaw at a slightly different angle posterior 

 surface of shaft with well developed longitudinal ridge. First, 

 second and third upper premolars two-rooted, small, their 

 points on level with those of incisors and inner cusps of 

 molars, their crowns separated from each other as well 

 as from canine and large premolar by narrow equal spaces ; 

 crowns rather higher than long, compressed, with slightly 

 developed posterior cutting edge, narrowly triangular in outline 

 when viewed from the side, the first more slender than the 

 others, the second and third with slight though evident postero- 

 external angle on cutting edge. Fourth premolar essentially 

 like the other three in form, but much larger and three-rooted, 

 the length of crown greater in proportion to height ; no secondary 

 cusps. Lower premolars two-rooted, similar to the upper teeth 

 in form, the second and third the same size as smaller upper 

 premolars, the first nearly as large as pm i , but narrower, 

 owing to absence of third root, the fourth intermediate. Upper 

 molars with crowns much wider externally than internally, 

 and completely divided into two unequal sections by a deep 

 longitudinal groove passing between protocone and bases of 

 paracone and metacone. Protocone large, its posterior com- 

 missure extending in line parallel to sagittal plane, and ending 

 abruptly at posterior edge of crown, near which it is slightly 

 thickened, its anterior commissure similar though shorter, but 

 usually showing some trace of thickening,* particularly in m 2 . 

 Paracone and metacone sub-equal in m 2 and m 3 , the metacone 

 the larger in the former, the paracone in the latter. In m 1 the 

 metacone is about double the size of paracone, and is the 

 largest and highest cusp of the upper molar series, its posterior 

 cutting edge and long commissure functioning with similarly 

 enlarged protoconid of m 2 . Styles and outer commissures well 

 developed in m 2 and forming a distinct VV"P a ttern ; mesostyle 

 entire or with apex slightly notched. In m 1 the parastyle is 

 reduced to a minute though usually evident cusplet on the 

 cingulum, and the mesostyle to a thickening or angle in 

 commissure connecting the two main cusps ; metastyle well 

 developed.f In m 3 the parastyle, mesostyle and their commis- 

 sures are well developed, metastyle and fourth commissure 

 absent ; mesostyle with apex usually bifid. Middle lower molar 

 largest, its protoconid the highest cusp in the series. First lower 

 molar broader posteriorly than anteriorly, second and third 

 slightly broader anteriorly than posteriorly, the two triangles 

 essentially alike in form. Metaconid of m 1 low, scarcely more 



* The thickenings vary considerably in different individuals. Occasion- 

 ally they are obsolete, but more frequently they are so well developed as 

 to form an evident protoconule and metaconule, the latter always the 

 larger of the two. 



t In this tooth there is no anterior V, the outer surface of paracone 

 essentially resembling that of pm' except for its smaller size. 



