OF MULTIVALVE SHELL-FISH. 159 



plenty, never removing from its narrow manfion ; thefea-water that en- 

 ters by its little gallery fatisfies its wants, and, witliout any other food, 

 it grows from feven to eight inches long, and thick in proportion. Their 

 fhell grows on them in the body of the rock. Thefe fhells take different 

 forms, and are compofed of a different number of valves, from three to 

 twelve ; fometimes the Ihell refembles a tube, with a hole at each end, 

 one for the mouth, and the other for voiding the excrements. Many of- 

 ten meet in the heart of the rock, and frequently break in on each other's 

 retreats. Whether by accident, or of choice, cannot be determined ; they 

 are mod commonly found in numbers in the fame rocki and fon>ctimes 

 above twenty within a few inches of each other. 



Xx 2 SURVEYS 



