Oysters and Scallops 



91 



act as scaveno^ers, Amonoj these are tlie little 



Porcelain-crab {Porcellana longicornis) and a marine 



worm (Polynoe). The Hermit - crab 



who lives in cast-off whelk-shells has 



similar messmates who do their best 



to keep the house clean for their 



host. 



This family also contains the Wing- 

 shell (Avicida Jdritndo), one of the 

 Pearl - oysters, and closely allied to 

 Pinna. It is like a small Pecten 

 whose hinder " ear " has grown to an 

 inordinate length, so that it resemljles a wing rather 

 than an ear. Its home is in the Mediterranean, but 

 it is occasionally taken on our southern shores, 

 perhaps being brought hither by currents in its earlier 

 stages. Several fishes, crabs, and jelly-fishes also 

 make their way from the Mediterranean to the coasts 

 of Cornwall and Devon. 



Gaping File-shell • 

 interior 



