Cowry and Pyramid-shells 



243 



(C. Tiiacand recti) is a much smaller and more delicate 

 species, found only on muddy sand off Shetland in 

 from 60 to 80 fathoms of water. The five points 

 from the mouth of the shell are relatively longer and 

 more distinct, the one that is nearest the spire often 

 exceeding it in length and running parallel with it. 

 The colour is paler, so is that of the animal. 



A more striking object-lesson in tlie evolution of 

 shell - structure is afibrded by the three British 

 members of the Cowry family (Oyprceidce), each of 

 them representing a separate genus. In all of them 

 the mantle is furnished with a pair of large side -lobes 

 which fold over the shell and almost meet above it. 

 The mouth of the shell is mostly as long as the shell, 

 and is not closed by an operculum. The animal has 

 a short muzzle, a broad foot with a squarish front, 

 and a long siphon. They are carnivorous, feeding 

 upon zoophytes, etc. Of these three forms the 

 Smooth Margin-shell (Erato kevis) best illustrates 

 our meaning. It will be seen that 

 the body- whorl is three or four times 

 longer than the remainder of the 

 shell, and that the mouth is almost 

 as long as this whorl. The lip of 

 this is at first quite thin and sharp- 

 edged ; then it is turned in a little 

 but still has a plain edge, but after- 

 wards it is considerably thickened 

 and becomes toothed on the inner 

 margin. Now the animal — which 

 is of a lively disposition — does 

 not permit us to see much of this white shell when 

 he is on active service, for the mantle-lobes are 



Margin-shell — 

 from above and below 



Margin-shell and animal 



