198 CONTRIBUTIONS 



much, from any species, fossil or recent, which has come 

 under my notice. It possesses transverse folds on the sides, 

 which lie closely to, and are beautifully parallel to each 

 other. These terminate in a smooth plane, on the umbonial 

 slope, which is flattened. A straight furrow, or channel, 

 passes along the posterior dorsal margin, in which are striae, 

 slightly oblique. The posterior series of teeth, as far as it 

 exists in this fragment, is straight, and possesses nineteen 

 angular teeth. From the appearance of this part of the 

 series, I should not be surprised if it possessed almost as 

 many more. The substance of the shell is thick, and it is 

 suspected, that when found perfect, it will prove to be the 

 largest species yet described. This fragment certainly 

 warrants such a conclusion. 



JV. carinifera. Plate 6. Fig. 212. 



Description. Shell triangular, inflated, deeply truncate 

 behind, minutely and concentrically striate, furnished with 

 an elevated sharp carina on the umbonial slope ; substance 

 of the shell thick ; lunule cordate ; beak high, incurved 

 and recurved ; posterior slope irregularly flattened, nearly 

 circular, and furnished with indistinct longitudinal and 

 transverse stria? ; anterior series of teeth short, consisting of 

 five teeth, and forming a sharp angle with the posterior 

 series ; teeth rather large, angular ; fosse t placed above the 

 teeth, at the point of the beak ; nacre not pearly. 



Diam Length .... Breadth .... 



The lower figure represents the posterior slope. 

 Observations. It is to be regretted that the description 



