BUCCINUM WHELK. 83 



at intervals by curved ridges which are the per- 

 manent margins of the former apertures, and are 

 interesting, as marking clearly the various stages 

 of the shell's increase. The Helmets are very 

 common, and many are remarkable on account of 

 their great size and solidity : one species (the Buc- 

 cinum Cornutum) is more than a foot in length. 

 The Helmets are handsome shells and are often 

 used as ornaments in rooms. They are found 

 mostly in tropical seas, distant from the shores, 

 in sandy bottoms where the animal buries itself 

 in search of prey. They form the modern genus 

 Cassis. 



The most beautiful shells of this genus are 

 called Harps ; * they have an elegant shape, rich 

 tints, and usually a glossy surface ; their form is 

 oval, and spire short, the aperture is large, and 

 notched at the base ; the inner lip is spread over 

 a portion of the body whorl, the outer lip is 

 thickened and rolled outwards. The animal pro- 

 duces a thickened revolute lip at each period of 

 its growth, and thus forms a number of elevated 

 ridges on the shell. Such marks of increase are 

 observable in many other marine shells, and in 

 a few land species ; but in none are they more 

 numerous than in the Harps : giving them a very 

 rich and pleasing appearance. The Harps are 

 found in ' the seas of hot climates, particularly 

 near the Isle of France. The genus they now 

 form is called Harpa. 



* Plate III. fig. 2. 

 G 2 



