194 NATURAL HISTORY OF OUR SHORES 



Its food in a state of nature consists of the spores of 

 sea-weeds, minute, floating plants, and the embryos and 

 Iarva3 of marine animals. 



Tn " layerings " near populous towns, in the estuaries 

 of rivers, etc.. its menu is unavoidably more varied. 



The above description applies to our common round 

 oyster (Ostrea edulis). In the mussel-shaped or " Ameri- 

 can " oyster (Ostrea virginea) the reproduction is 

 different, the fertilisation of the eggs, and subsequent 

 development of the young, taking place in the water, 

 and not within the parent. 



Anomia ephippium (the " Saddle Oyster "). This is often 

 mistaken by many for the young of the edible oyster, 

 which it somewhat resembles in general outline. 



The shell in this genus is thin, and irregularly waved, 

 with pearly tints. It is very common, and is frequently 

 attached to the shells of ordinary oysters, also to the large 

 pecten. It is found at extreme low water, but is more 

 usually taken with the dredge. Its method of attachment 

 is peculiar. The lower shell is perforated near the hinge, 

 and a solid little block of carbonate of lime, in the form of a 

 collar stud, is there secreted, one end firmly fixed to such 

 object as forms the base of attachment, the other within 

 the mollusc, so that the latter can be moved about, as if 

 on a ball-and-socket hinge. It is about two inches across 

 when full grown. 



A second species (-4. patelliformis) is found on our coasts, 

 but not so frequently as the former. 



Pecten maximus (the " Common Scallop "). This is 

 common all around our shores, from the lower littoral 

 zone to deep water, wherever the bottom is suitable ; 

 rough, gravelly ground, clean sand, and Zostera fields 

 being its usual habitats. 



The pectens are not fixed, but have power of a certain 

 amount of locomotion. This is effected by the alternate 



