CARDIUM. 289 



soft, the shell is thinner, and the posterior side has a 

 tendency to become elongated and more wedge-like 

 than usual. In exposed and rough seas, where the 

 ground is harder, the shell is thick and globular. In 

 certain localities the inside is of a rich purple colour. 

 The largest specimens I have seen came from Unst 

 and Stornoway, and the next in size from Appledore 



in North Devon and the Scillv Isles. Some of these 



t/ 



examples measure 2 J inches in breadth. Distortions 

 are not unfrequently met with. The most remarkable 

 are as follows : — inequivalve, the left valve being much 

 smaller than the right, and nearly flat ; divided into 

 two lobes by a constriction in front ; resembling a 

 Cardissa, the anterior side being squeezed in and show- 

 ing a large lunule; and one shell piled on another, 

 and apparently growing out of it. Irregular pearls are 

 occasionally formed. A specimen of C. edule in Mr. 

 Norman's cabinet, found bv Mr. Cocks at Falmouth, 

 contains a massive secretion of this kind, which occu- 

 pies nearly one-half of the inside. It proceeds from 

 under the beak, and looks like a huge wen. The animal 

 seems to have suffered no further inconvenience from 

 the excrescence than being obliged to extend its shell 

 in front, so as to make up for the space lost at the back. 

 I have likewise a large button- shaped livercolour pearl 

 which was taken from a common cockle in the act of 

 being eaten at breakfast. Young shells are frequently 

 round, or longer than broad, and are indistinctly angular 

 on each side. In a still earlier stage of growth they are 

 very prettily variegated, and liable to be mistaken for 

 C. fasciatum ; but they never have the oblique contour 

 or the polished ribs of that species. 



I hope I shall not be accused of undignified trifling, 

 or of venting platitudes, if I say a little more about the 



o 



