180 BIVALVES. 



nishing powers of locomotion, considering the 

 inferiority of their organization ; but dexterity 

 and ingenuity frequently compensate for natural 

 deficiency. They have the power of progressive 

 motion, both on land and in the water. When 

 the animal happens to be left on the shore by the 

 retiring tide, it opens its valves to their full 

 extent, and closing them with great muscular 

 power, is thrown forward five or six inches by a 

 sudden leap. In this manner it reaches the sea ; 

 should the weather be calm, it raises one of its 

 valves, which catching the breeze, acts as a kind 

 of sail, while the other resting on the surface, 

 supports the floating animal ; when danger threat- 

 ens, the shell is closed, and sinks securely to the 

 bottom of the sea. Many of the Pectens possess 

 the power of forming threads, by which they an- 

 chor themselves to floating timber, and by this 

 means find protection when the sea is agitated by 

 storms and tempests. These varied means of 

 escaping danger are no doubt afforded as a neces- 

 sary protection against their numerous enemies. 

 The pilgrims who in former days visited Jerusa- 

 lem, to pay their devotions at the holy sepulchre, 

 on their return wore these shells in their caps as 

 trophies of their achievement in crossing the sea 

 for this sacred purpose ; and in commemoration 

 of this superstitious act of devotion, it was often 

 granted them to have Pectens engraved in their 

 coats of arms, that a record of their religious zeal 

 might be handed down to their posterity. 



