l86 BY THE DEEP SEA. 



The Mollusca that actually live between tide-marks, though 

 numerous as individuals, do not represent many species ; but 

 those of which we may find the recently-vacated shells, thrown 

 up by the tide from greater depths, will total up to a consider- 

 able number. The bivalves must be sought for on sandy 



SPINY COCKLE. BANDED VENUS. 



beaches and mud flats, especially at the mouths of rivers. 

 Most of them are burrowers, excavating a way by means of 

 the powerful foot with which they are provided. This instru- 

 ment is well seen in the Razor-shells (Soleii), or the Cockles 

 (Cardiuni], where it reaches extraordinary development. Even 

 where the animal lives far beyond our limits in deep water we 



