82 UNIVALVES. 



bous ; aperture ovate, effuse at the base, ending 

 either in a notch, or a short canal abruptly 

 curved and turning to the left, that is, from the 

 outer lip ; columellar lip flattened. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The characters which distinguish this genus 

 do not always occur in each species. The most 

 invariable mark of distinction is the direction of 

 the canal ; and should this fail, as is the case in 

 a few instances, the thick gibbous form or the 

 flattened columellar lip will still point out the 

 proper situation of the shell to be amongst the 

 Buccina. 



One division of this genus is known by the 

 common name of Tuns ; their scientific name 

 is Dolium. These shells are thin, brittle, turbi- 

 nate, of an inflated or globular form, transversely 

 ribbed, the aperture is large, and has a notch 

 at the base. The type is the Buccinum Dolium.* 



Many of the Buccina are called Helmets, f 

 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 revolute,J and often dentated ; 



* Plate III. fig. 1. t Plate III. fig. 3. 



$ Revolute, rolled back. 

 Dentated : toothed, frpm Latin, dens, a tooth. 



