305 

 CAMEI\ELLA ? COSTATA. (N. sp.) 



Fig. 296. 



Description. Broad ovate, greatest -width about the mid-length, uni- 

 formly convex, with from ten to twelve strong, angular undivided ribs, 

 which extend to the beaks. 



The best preserved specimen of this species that has been collected, is 

 partly imbedded in the matrix. It is transversely ovate or sub-circular, 

 the width one-fourth greater than the length, the sides and front uniformly 

 rounded, rather strongly convex, the greatest elevation at one-fourth the 

 length from the beak ; umbo broadly rounded. It appears to be a dorsal 

 valve. 



Length 6J lines ; width 8 lines. 



It is quite uncertain that this species is a true Camerella. It may be 

 congeneric with Porambonites Ottawaensis (ante, p. 240). 



Locality and Formation. Stanbridge, range 6, lot 20 ; Quebec group. 



Collectors. J. Richardson, T. C. Weston. 



CAMERELLA POLITA. (N. sp.) 



Fig. 297. 



Description. Shell ovate, smooth and moderately convex, greatest 

 width at about one-fourth the length from the front margin, thence taper- 

 ing with gently convex sides to the beaks ; front angles and margin rounded. 

 Dorsal valve most convex just in front of the umbo ; beak incurved down 

 to the hinge. Ventral valve less convex than the dorsal ; beak /small, 

 pointed, a little elevated above the hinge. 



Surface smooth. 



Length of largest specimen collected 3 lines ; width about the same. 



This species has nearly the same form as C. Ireviplicata, but differs 

 therefrom in being smooth, in being less convex, in having the front mar- 

 gin thinner and usually more rounded. The form varies from ovate to 

 sub-circular. The young individuals of C. breviplicata have two or three 

 incipient folds in the front margin by which they may be readily dis- 

 tinguished from this species. 



Locality and Formation. Stanbridge, range 6, lot 20, and on the 

 upper end of the island of Orleans ; Quebec group. 



Collectors. T. C. Weston, E. Billings. 



