NATURAL HISTORY. 4C? 



careful examination. Every one who has seen a living limpet 

 knows how firmly it fixes itself to the rock. This is done by 

 the inhabitant creating a vacuum on the under surface of its 

 body, which causes the pressure of the atmosphere to keep it 

 so tightly fixed to the rocks, that a blade of a strong knife is 

 required to detach it. Frequently the margin of the shell 

 adapts itself to the shape of the substance to which it adheres, 

 proving that it must remain fixed in the same spot for a long 

 time, and rendering it difficult to imagine from whence it can 

 obtain sufficient nourishment to support life. 



Sometimes a large shell may be picked up covered with 

 limpets, that adhere firmly to it in spite of the rolling of the 

 waves, and the tossings about to which it must necessarily bo 

 subjected. 



Order.. CONCHIF%RA.(Gr. Ko-yxv, a Mussel-shell; 0/xj, I bear.) 

 Family . Pectinidoe. (Lat. Pecten a Scallop.) 

 PECTEX. 



Jacobaeus (Lat. from a proper name), the Scallop. 



We now arrive at the BIVALVE MOLLUSCS. It has been 

 already stated that the Bivalves arc all aquatic. These crea- 

 tures are enabled to keep their shells firmly closed by means 

 of a powerful muscle. Those who have attempted for the first 

 time to open an oyster, must be convinced of the strength of 

 this muscle. The two shells are united by a powerful and 



