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SHELLS. 



Shells of a species, one might almost say, are generally somewhat similar to each other, 

 Nature as a rule approving of symmetry, yet with them as with others of her productions there 

 are many exceptions. If we take the large scallop-shell or pecten, we find the two valves 

 unequal in size, like its ally the oyster. In it the flat valve being coloured and the hollow one 

 plain, it would lead one to suppose the hollow one rested at the bottom of the sea, but with the 

 oyster I think the flat valve rests on the bottom of the sea ; but though the two creatures 

 resemble each other in some respects, why should one have a symmetrical covering and the 

 other quite the reverse ? No doubt the oyster frequently attaches itself to some foreign body, 

 and the shell takes the form of the rock or other substance to which it adheres. I once 

 had an oyster which when small had fixed itself inside the bowl of a tobacco pipe, the 

 shell had become much enlarged, but, being tightly fixed in the pipe, it had become distorted. 

 Then again, observe the form of the smaller scallop-shell or pecten, and you find the two valves 

 both hollow; but why are the pectens so perfectly formed, and the oysters so irregular even 

 when not attached to any substance? We have a pecten on our shores which, to a certain 

 extent only, keeps its form and streaked marks, but it varies in shape according, I presume, to 

 the locality in which it lives ; in this respect somewhat resembling the spondylus which often 

 fixes itself upon coral and suits the shape of its shell accordingly. Any one not accustomed to 

 see oysters on the beds would scarcely notice them, so like are they to the ground on which 

 they lie the small stones, amongst which they often are, being covered with similar substances 



