PEARL SHELLS. 251 
Mr. Couch, in his “ Fauna of Cornwall,” observes 
that “this species is found in the greatest abun- 
dance at the distance of from three to six leagues 
south of the Deadman Point, where they stud the 
bottom in multitudes, with only two or three inches 
of the pointed end inserted into the soil. It is 
common for the line or hook to become entangled 
among these shells, and powerful effort is required 
to drag them from their attachment, which is 
only effected by breaking the byssus, or tearing 
away the ground to which it 1s attached. In the 
latter case a rich harvest of shells is often afforded, 
but the pointed end of the Pinna is usually broken 
off by the violence. It is perhaps owing to the 
different degree of solidity of the ground, that 
the shells living in the deeper water are so much 
less buried than those of which Montagu speaks, 
and one of the consequences may be a greater 
degree of motion in the shell. Montagu observes 
that the exposed end cannot be closed by art, but 
the animal is capable of effecting it; and obser- 
vation has taught me, that this is its method 
of obtaining food. In its ordinary position this 
opening is about two inches wide, exposing the 
contained animal, which occupies but a small por- 
tion of the cavity, and seems to offer itself a 
prey to the first creature that may choose to devour 
it. Some fish is thus tempted to enter, but the 
first touch within is a signal for its destruction. 
The shell closes not only at the side but at the top, 
the latter action being effected by a separation of 
the pointed ends, and the captive is either crushed 
to death, or soon perishes from confinement.” 
