104 



SHELLS AND SHELL-FISH. 



family first engaged our attention, we imbibed a notion 

 that the formation of the spire was the chief, if not the 

 only, character upon which they should be arranged : we 

 soon, however, threw aside this, and fancied the same 

 importance attached to the number of plaits : equally dis- 

 satisfied with this theory, we finally resolved to combine 

 all these characters, without giving to any one a para- 

 mount importance : having done this, we soon perceived 

 that these groups turned out to be representations of all 

 those in the entire family ; and this discovery prevented 

 our falling into many errors, which would otherwise 

 have been inevitable. We may now consider each of 

 these genera in further detail. 



(94.) The pre-eminent types of the genus Valuta, for 

 reasons subsequently stated, are such shell-fish as have the 

 spire small, and so slightly developed, as to be all but 

 obsolete. This we see more especially in Voliita Nep- 

 tuni, Porcina, and CymUum (fig. 9. «) where nearly the 



whole shell being enveloped, as it were, in the body-whorl, 

 gives to it, in all but the plaited pillar, the perfect ap- 

 pearance of a Bulla. The very slight elevation of the 

 spire is, therefore, one of the typical characters of this 

 genus ; but it is not the only one : the spiral whorls, 

 which end in the apex, whenever they are developed, 

 are remarkably thick, and are always perfectly smooth, 

 although the body-whorl may be coronated ; whereas in 

 the next genus, Cymbiola (C vespertilio, fig. 9. &), these 

 spiral whorls are always plaited (c). There is a solitary 



