20 WEST COAST SHELLS 



dant than they are at present. In some parts of 

 our country great masses of rock may be found which 

 are made up ahnost entirely of these fossil shells. 

 But now it is different, and so we turn to another 

 class of animals, which seem to be in their full glory 

 at the present time. Where we had only halt a 

 dozen species of lamp-shells to describe, we shall 

 find more than a hundred of the bivalves to claim 

 our attention. 



We call them bivalves because each animal is pro- 

 tected by two valves, or half shells, which are hinged 

 together at the top and which open somewhat at the 

 bottom. Clams, oysters, scallops, and cockles all 

 belong to this division of the mollusks. Their real 

 name is Pelecypods, which means hatchet-footed 

 creatures, since many of them have a burrowing 

 organ, or foot, as it used to be called, shaped some- 

 what like the blade of a hatchet. To be sure some 

 use this foot to jump with, and others modify it into 

 a kind of finger, and still others have no foot at all 

 to speak of, and yet, in their organism they all show 

 many signs of resemblance and all have the two 

 shells, a right and a left valve. None of them are 

 blessed with a head, a lack of which organ any of 

 us would find very embarrassing; but not so our 

 happy clam, for never having possessed a head he 

 feels no use for one. 



So he digs a burrow with his hatchet-shaped foot 

 and pulls himself down into it and feels reasonably 

 safe. To be sure he needs food and some kind of 

 breath, but he is so wonderfully made that he has 

 little trouble in obtaining either, for in fact they 



