166 CONTRIBUTIONS TO CANADIAN PALEONTOLOGY. 



Pteria (Oxytoma) Corneuiliana, d'Orbigny. 

 Plate 23, figs. 1, 1 a and 1 b. 



Avictila Corneuiliana, d'Orbigny, 1845. Pal. Franc, Terr. Cret, tome III, p. 471, 

 pi. 389, figs. 3 and 4. 

 " " Pictet and Campiche. 1868-71. Paleont. Suisse., Bescr. 



des foss. du Terr. Cret. des Env. de Ste. Croix, tome III, p. 

 66, pi. 1.52, figs. 1-4. 



A few detached and more or lens imperfect valves of a shell which 

 cannot at present be satisfactorily distinguished from the above named 

 European species. The following is a description of the specimens 

 collected by Mr. McConnell, as they appear to the writer. 



Shell rather large, veiy inequilateral : left valve compressed but 

 somewhat tumid in the umbonal region, at least in some specimens ; 

 right valve nearly fiat ; marginal outline of the valves, apart from the 

 two wings, obliquely and broadly semiovate, the maximum length 

 very slightly exceeding the greatest height. Anterior side very short 

 and broadly rounded; posterior side produced and much longer, as well 

 as more narrowly rounded at its termination, than the anterior ; pal- 

 lial border convex ; hinge line apparently straight both behind and in 

 front of the beaks ; anterior wing small and triangular ; posterior 

 wing apparently short and extending to less than half the distance 

 from the beak to the farthest termination of the valve behind (at least 

 in the most perfect left valve collected) but much longer proportion- 

 ately in the most perfect right valve, its posterior mai'gin concavely 

 excavated; beaks small, scarcely projecting above the highest level of 

 the hinge line, and pilaced considerably in advance of the midlength. 



The surface markings of the largest and most perfect of the left 

 valves collected consist of seventeen narrow but prominent, distant 

 and simple radiating ribs, and these are separated from each other by 

 broad flattened spaces which bear still narrower and much less promi- 

 nent radiating raised lines. The principal ribs seem to have projected 

 beyond the outer margin of the valve as short free spines, and between 

 each pair, on and around the said margin, from five to six radiating 

 raised lines can be counted. 



The right valve is marked only by numerous fine radiating ribs, 

 which are much smaller than the large ones in the opposite valve, as 

 well as nearly equal in size and placed comparatively close together. 



Hinge dentition and muscular impressions of both valves unknown. 



Maximum length of the largest specimen collected (a left valve) 

 sixty-eight millimetres ; greatest height of the same sixty-one mm. 



