BIVALVE MOLLUSCANS. 241 



feet, they are often severely wounded by the 

 sharp edges of their shells. The animal descends 

 to the bottom of its burrow when the tide retires, 

 and there remains till its return when it rises 

 again. In order to take it, the fishermen are 

 accustomed to cast into its retreat which always 

 remains open for respiration, and which is indi- 

 cated by a little jet of water a very little salt, 

 this probably deceives the razor-fish and causes 

 it to ascend, thinking the tide returned. They 

 bury themselves with wonderful celerity by the 

 rapid action of their foot, and mount again by 

 the combined action of that part and their smooth 

 valves. The former is cylindrical and ends in a 

 spherical summit of larger diameter than the 

 rest of the foot. 1 



The common cockle 2 is also a borer. Mr. 

 Osier, in a very interesting paper in the Philo- 

 sophical Transactions for 1826, has described 

 the way in which they bury themselves. The 

 foot of the cockle, he observes, is very strong 

 and .stiff, and is the instrument by which they 

 principally perform this operation ; but to look 

 at it when unemployed, we cannot readily con- 

 ceive how it can make a burrow capacious 

 enough for so large a shell. Its point, indeed, 

 is solid, and a viscid secretion from its surface 

 enables it to fix itself more firmly in the sand, 

 but this alone is not sufficient to accomplish this 



1 PLATE V. FIG. 1. 2 Cardium edule. 



VOL. i. R 



