12 CANADIAN FOSSILS. 



R. LAPICIDA, N. Sp. 



Plate II. Figures 1-3. 



R. uncialis, discoidca, lenticularis, margine acutissimo : anfractibus 4 lavi- 

 gatis, Supra planis, atque suturis inconspicuis, subtus convexis ; 

 umbilico angusto rotundato ; ore ovato acutissimo. Diameter, 10 

 lines ; alt., 5£ lines. 



This elegant shell a good deal resembles the R. staminea of Hall's 

 work (Pal. New York, vol. i., pi. 6, fig. 4, 5), from which it is readily- 

 distinguished by the less raised spire, flatter base, and larger umbili- 

 cus. It is altogether a flatter and smoother shell, the lines of growth 

 not sharp and regular, and on the upper surface there is no concentric 

 ridge to interrupt the backward course of the striae. And comparing 

 it with other American species, the R. (Maclurea) labiata, Emmons, 

 and the very similar R. (Pleurotomaria) lenticularis of the same author 

 (not of Sowerby), have both more convex bases, the outer face of 

 the whorl below being almost vertical in the former, and at least 

 convex in the latter, instead of first concave and then prominent. 

 The umbilicus in both is too large for ours. 



The whorls of the spire slope regularly to the apex without inter- 

 ruption at the sutures, the last whorl excepted, which descends a 

 little beneath the margin of the preceding. The edge is very acute. 

 The under-side, only a little more prominent than the spire, is first 

 concave beneath the keel, then convex towards the deep narrow 

 umbilicus with its incurved sides. The striae of growth are more 

 conspicuous below than above. The rounded sides of the umbilicus 

 easily distinguish R. lapicida from the next described species. The 

 inner lip is prominent and a little reflexed. The angle of the ovate 

 mouth very acute, and the notch deep, but the lower margin does 

 not project greatly forward. 



A general resemblance to Helix lapicida suggests the name. 



Locality. — Allumette Island. 



R. APERTA, N. Sp. 



Plate II. Figure 4. 



R. semiuncialis, anfractibus 4 inswper depressis, subtus perangulatis : umbi- 

 lico latissimo infundibulato ; ore rhomboideo. Diameter, 6 lines ; 

 alt., 3 lines. 

 The whorls are of about the same proportionate width as in the 



