88 CONTRIBUTIONS 
about twenty-one, large, alternating with as many small 
ones, all imbricate ; beaks pointed. 
Diam. ..... Length 1.3, Breadth 1.3, ofan inch. 
Observations. 1 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 small 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. 
