88 CONTRIBUTIONS 



about twenty-one, large, alternating with as many small 

 ones, all imbricate ; beaks pointed. 



Diam Length 1.3, Breadth 1.3, of an inch. 



Observations. I know no species which this resembles 

 so much as the gracilis (Sowerby), from the Crag at Holy- 

 wells. It differs in having rather large ribs instead of 

 " many small longitudinal ridges." 



P. Lyelli* Plate 3. Fig. 67. 



Description. Shell longitudinal, rounded below, angular 

 above, compressed ; ears very unequal, having a channel 

 on the larger one ; substance of the shell thin ; ribs about 

 twenty-two, rounded, slightly imbricate ; beaks acutely 

 angular. 



Diam Length ,8, Breadth .7, of an inch. 



Observations. This species differs from the last described 

 in being more elongated, in having very unequal wings, in 

 having a channel on one wing, and in having no alter- 

 nate ribs. A single smaH valve accompanied this species, 

 which appears to be different, the ears being not quite so 

 unequal ; further specimens may prove it to be worthy of 

 a specific distinction. If so, I propose the name of mi- 

 nutus. 



* Named after the eminently distinguished geologist Charles Lyell. 



