88 THE ROYAL SOCIETY OF CANADA 



cardinal area the hinge line is curved on each side of the centre so that 

 the margin of the pedicle valve has two projections, which correspond 

 to embayments in the margin of the brachial valve. The pedicle open- 

 ing is small and apparently transversely elongated. The beak of 

 the pedicle valve is prominent and slightly incurved, but not so as to 

 project over that of 'the brachial valve. There is no distinct sinus, 

 but the forward part of the pedicle valve is of flatter foim in the mesial 

 portion than at the sides, producing a broad upward flexure of the 

 anterior margin. The brachial valve is more convex toward the front 

 than the pedicle, but can scarcely be said to have a distinct mesial 

 fold. Both valves appear to have been marked by numerous rather 

 faint concentric lines of growth interspersed with stronger ones at 

 intervals of about two millimetres, and have also on the interior 

 numerous fine radiating striae. Plications are almost absent in this 

 shell except at the lateral margins where two or three faint folds can 

 be traced about two thirds of the distance from the margins to the 

 beaks. The anterior margin is wavy as viewed from in front, but 

 the plications cannot be traced backward from the edge except the 

 mesial one in the brachial valve, which extends as a shallow groove 

 nearly to the beak. 



Rhynchonella non-sinuata (sp. nov.) cf. R. plicatilis (Sowerby) * 

 (Plate III, Figs. 8a, b) 



R. plicatilis is reported by Eichwald as occurring in the Aleutian 

 Islands, and several specimens in the present collection seem more 

 closely related to this species than to any other whose description is 

 known to the writer. 



The specimens are roughly sub-trigonal, with concave postero- 

 lateral margins and an outline which is otherwise transversely ellip- 

 tical. The greatest width is 18 to 19 mm., the length from beak to 

 anterior margin 15 mm, the convexity 7 «5 to 9-5 mm., about equally 

 divided between the two valves. There is no distinct sinus or mesial 

 ridge in either valve, but the anterior margin is broadly curved toward 

 the brachial side. The beak and umbo of the pedicle valve are rather 

 prominent, and the curvature of the surface from the centre of the 

 umbo to the lateral margins is resupinate. The plications are well- 

 marked, extending to the beaks, and are from fourteen to sixteen in 

 number. The brachial valve has a somewhat bolder arch, which 

 extends from side to side without resupination. 



*Sowerby, Min. Conch., Vol. V, p. 167, table 503, fig. 1; Davidson, British 

 Cret. lirachiopoda. Pal. Soc, Vol. 1, 1852, p. 75, Plate X, figs. 37-42. 



