38 CARDIADiE. 



hyaline valve ; a faint brown line runs along- its upper and 

 lower surface. The foot is long and powerful, securiform, 

 and thick, pointed at its extremity, of a red-flesh colour, 

 except its apex, which is white, and a margin, as it were, 

 of fulvous hue. The coloured portion presents a shagreened 

 aspect under the lens, and depends upon an exceedingly 

 thin epidermis which is rubbed off by the slightest touch, 

 exposing pure white below it. The branchiae are of a pale 

 brown colour and triangularly suboval shape, with fulvous 

 or dark-brown margins and tips. The iipper leaflets are 

 smaller than the lower, and hang subvertically, with trans- 

 verse striee more visible on the outer than on the inner sur- 

 faces, being the reverse of the two palps on each side, which 

 are smooth on the outer area, and striated within, trian- 

 gular, very large, and pointed. 



The Card'mm Norvegicum lives on a sandy or gravelly 

 bottom at a depth usually of from fifteen to thirty fathoms. 

 Dead valves have been taken as deep as eighty fathoms, and 

 are not unfrequently cast on shore by the waves. The 

 dredge and the trawl are its most efficient captors, and it 

 ranges to a considerable distance from land. It is not 

 habitually gregarious, often solitary. It is very active, and 

 capable, by means of its large and powerful foot, of effect- 

 ing considerable leaps, often springing out of the vessel 

 in which it is placed when in captivity. It is so generally 

 (though often sparingly) distributed around our shores that 

 we must consider it a common species, and need not enu- 

 merate localities, being absent from none of our local lists, 

 either of eastern or western origin. Northwards it ranges 

 to Norway, southwards to the Mediterranean ; and as a 

 fossil is known in deposits of pleistocene age. 



