84 LESSON XI. 



tened columella still points out the proper situa 

 tion of the shell to be among the Buccina. 



One division of this genus is known by the 

 common name of Tuns. These shells are thin, 

 brittle, turbinate, of an inflated or globular form* 

 transversely ribbed, and have a notch at the 

 base of the aperture. The type is the Buc- 

 cinum Dolium.* 



Many of the Buccina are called Helmets, 

 and are distinguished by their inflated, turbinate 

 form, and by their short beak abruptly reflected ; 

 their columellar lip is thickened and spread over 

 the body whorl, forming a flat expansion ; their 

 outer lip is also re volute,")* and often dentated ; J 

 their spire is retuse and marked at intervals by 

 curved ridges, which are the permanent 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 size 

 and solidity. One species (the Buccinum Cor- 

 nutum) is more than a foot in length. It is a 

 handsome shell, and often used as an ornament 

 in rooms. It is found mostly in tropical seas, 

 distant from the shores, in sandy bottoms where 

 the animal buries itself in search of prey. 



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, spire short, aperture large, notched at the 



* Plate III. figure 1. t Revolute, rolled back, 



J Dentated : tooth, from Latin, dens-, a tooth. 

 $ Plate HI. figures. 



