WHITEAVES.] CRETACEOUS FOSSILS FROM MANITOBA. 193 



one well developed denticle on each side of its base: root deeply but 

 narrowly and not at all angularly forked, the two radicles being 

 nearly parallel and but slightly divergent, with their ends narj-owly 

 rounded. Central cusp of the crown slightly recurved, conical and 

 rather slender, its height, as measured on the longer and flatter of the 

 two sides, being mf)re than twice its breadth at the base, which lattui-, 

 as viewed edgeways, is oblique, the plane face descending fai- below 

 the convex. Outer coronal face nearly flat, but marked with a shallow 

 longitudinal depression or faint gi-oove on each side, next to the lateral 

 margins, the intervening central space being nearly flat or very slightly 

 convex, — but its basal portion is ornamented also with a few acute and 

 longitudinal plications of unequal size and length, the two nearest to 

 the centre being longer and larger than any of the others. Inner coro- 

 nal face convex, especially below, the greater part of its surface marked 

 by numerous (about sixteen; irregulav and longitudinal, but not quite 

 straight, acute ridges or plications, some of which are comparatively 

 short and do not extend the whole length of the cusp, while those that 

 do usually bifurcate or trifurcate at the base. When examined with a 

 lens, however, this plicated area is seen to be bordered with a narrow, 

 smooth space, on both sides and next to the lateral margins. Cutting 

 edge thin and sharp, with a minute tubercle at the base, on each side. 



The lateral denticles are triangular, with their apices slightly diver- 

 gent and pointing upward aud outward : their height and bi'cadth are 

 about equal. On their outer side they are nearly flat and on their 

 inner convex, while the ornamentation on both sides of the surface is 

 essentially similar to that of the central cusp of the crown, though the 

 plications on their inner or convex side, while equally well marked, 

 are of course not nearly so numerous. The root also is nearly flat on 

 its outer side, but on its inner face it is everywhere more or less con- 

 vex, and immediately under the base of the central cusp it swells up 

 into an elevated protubeiance with a rounded summit. 



The foregoing description is baaed upon two nearly perfect detached 

 teeth collected by Mr. Tyri'ell, in 1887, at Eolling River, two miles 

 above Heai-t Hill, from the Niobrara group or uppei' portion of the 

 series. The dimensions of one of these specimens, which is figured on 

 Plate 26, are as follows : entire height, from the base of one of the 

 radicles to the summit of the central cusp, eighteen millimetres; 

 breadth of the tooth, near the base of the root and below the two den- 

 ticles, nine mm. and a half; height of central cusji, ten mm. and a half 

 on the outer or flattened side and seven mm. and a half on the inner; 

 breadth of the same at the base, four mm. and a half. 



A few dental ci-owns of similar teeth were collccle<l by Mv. Tyj'rcll 

 in the same year at the Eolling Eivcr, in Township SG, liajige 2U W., 



