XIV INTRODUCTION. 



mal, plainly indicates, by the faintness of the tint, 

 that the colouring juice was wanting in that part. 

 It is a simple straight line, when the edges of the 

 wings are of the same configuration, but passes in 

 a sinuous, or waving, direction, as in the Cyprcea 

 Mappa, when the same edges are fringed, or irregu- 

 larly cut in their contours. 



There is a singular fact, noticed by Bruguiere, re- 

 specting the animal inhabitants of these shells. They 

 can quit their apartment at pleasure, and construct 

 a new one, whenever they find it convenient. This, 

 however, is never done but from necessity. During 

 the time the animal is completing its shell, it in- 

 creases in size, till at length it grows too large for 

 its habitation, which, when finished, remains per- 

 manent. Thus straightened for room, it is obliged 

 to quit its old dwelling, and build a new one of larger 

 dimensions, and better proportioned to the in- 

 creased size of its body. We are at a loss to say how 

 this operation is performed ; but it is probably a 

 matter of no great labour, since the body of the 

 animal is of a consistence between tendinous and 

 mucilaginous, of course not making any great re- 

 sistance to its passage through the mouth of the 

 shell ; for the foot and the two wings, which com- 

 pose by far the largest part of the bod} r , slip out in 

 a moment, with the greatest ease. This separation 

 of the animal from its shell is not difficult to con- 



