THE GREAT CLAM. 65 



of the shell near the hinge, an aperture, closed by a 

 kind of operculum or lid, formed at the dilated ex- 

 tremity of an internal muscle ; and it is by this part 

 that the animal fixes itself. In another, the beak of 

 the lower valve turns up, overhanging, in some degree, 

 the upper valve ; and in this beak is a notch or aper- 

 ture, through which the fixing tendon passes. What 

 an admirable instance have we here of variation in the 

 means, when required by circumstances, to gain the 

 same end ! Nor is this all ; it was necessary that the 

 valves should not be reversed : a tendon through the 

 lower valve secures this in the first of these animals ; 

 but in the second, when the overhanging beak would 

 interfere with this purpose^ the tendon issues from the 

 beak itself, so as to enable the animal still to fix itself 

 with the proper valve downwards. 



The great clam is a very remarkable creature. We 

 are told by Linneus, that one specimen weighed 498 

 English pounds ; that the inhabitant furnished 120 men 

 with provision for a whole day ; and that the sudden 

 closing of its valves was sufficient to snap a cable 

 asunder. A manuscript in the library of the late Sir 

 Joseph Banks, also notices the dimensions of a speci- 

 men brought from Sumatra, and preserved at Arno's 

 Vale, in Ireland : the weight amounted to 507 pounds ; 



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