THE MOLLUSCA. 123 



Single valves are common ; perfect double specimens 

 may sometimes be met with after high tides. 



Cardium edule (Common Cockle). A very common shellfish 

 about Southport at all times. In 1858, a cockle-bed 

 or " scour," as it is locally termed, was discovered about 

 five miles north-east of the town, where the cockles were 

 so numerous as to be literally shovelled up with spades ; 

 the yield for several months was from ten to fifteen tons 

 a-week. It is scarcely possible to realize the prodigious 

 numbers taken from the bank, as a ton contains about 

 80,000 individual cockles. 



Cardium Norvegicum. A small delicate-looking shell ; single 

 valves found upon corallines. 



LUCINID^E. 



Lucina leucoma. Extremely rare ; one or two single valves 

 only found. 



KELLIAD^E. 



Montacuta ferruginosa. Very rare, and single valves. A 

 small white, oval, semi-transparent shell, about three- 

 sixteenths of an inch long, generally stained with rust- 

 colour. This and the following species are found by 

 collecting and washing the sand and broken shell from 

 the ripple-marks and slopes of banks. 



Montacuta bidentata. Moderately common A minute white, 

 oval, almost transparent shell; about one-eighth of an 

 inch long. 



Mytilus edulis (Common Mussel). Common. Sometimes in 

 great numbers attached to pieces of wood or sea-weed. 



