MOLLUSC A. 



213 



of the shell ; the latter has " ears " or flat expan- 

 sions on each side of the hinge. They are some- 

 times called " sea butterflies/' ^ from the appearance 

 of the coloured valves when they move ; this they 



Fig. G5. — The Scallop Shell, Fecten opercularts, with ears of the two valves 

 differently shaped. 



do by a sudden hop that carries them some distance, 

 and is accomplished by the sudden opening and clos- 

 ing of the shell. Like the oyster, they have one 

 valve deeper than the other. The largest kind, Peeten 

 maximax, is as large as a large oyster : F. opercularis is 



' This name,. however, belongs properly to the Pteropods. 



