ITS BURROWING FUNCTION. 95 



made suddenly rigid, and the entire creature, mantle, 

 siphons, foot, shell and all, is jerked away in an un- 

 couth manner, " quite permiscous," as the fisherman 

 hard-by says, to a distance of some foot or more. But 

 the cockle can leap on occasion much more vigorously ; 

 one has been seen to throw itself clear over the gunwale 

 of a boat when laid on the bottom-boards. 



Thus we see one use of the hooked tip is to afford a 

 stronger spring ; but it has a more direct bearing on 

 the burrowing habits of the animal. Like all the rest 

 of its beautiful tribe, this species is a dweller in the 

 deep sand, into which it can penetrate with consider- 

 able power and rapidity. In order to do this, the foot 

 is straightened, and the sharp point is thrust perpendi- 

 cularly down into the wet sand. The muscular force 

 exerted is sufficient to penetrate the soft sand to the 

 whole length, when the point is suddenly bent sidewise, 

 thus obtaining a strong holdfast. The whole organ is 

 now strongly contracted in length, and the animal and 

 shell are dragged forcibly to the mouth of the burrow, 

 the edges of the valves downward and piercing the sand 

 a little way. The straightened point is then pushed an 

 inch or two farther down ; again hooked, and another 

 pull is made. The shell descends a little farther into 

 the yielding sand, and the same interchange of processes 

 goes on till the animal is sufficiently buried. To read 



