102 



SHELLS AND SHELL-FISH. 



PART I. 



(92.) The VoLUTiNJE, or volutes, are immediately 

 distinguished from the mitres by being more ventricose 

 shells, with a much shorter spire (as in Voluta Ollu, 

 fig. 8.), the apex or point of which is 

 more or less thick and papillary. These 

 characters are developed in their highest 

 perfection in the smooth and coronated 

 melon-shells, to which, as being the 

 pre-eminent types of the whole family, 

 we are compelled to retain the sub-generic 

 r\dimeoi Voluta. Nevertheless, these cha- 

 racters are greatly modified in the five 

 leading genera, which we characterised 

 and illustrated several years ago ; and time has only con- 

 firmed us in the views we then took on the subject. We 

 accordingly arrange the whole of the Lamarckian volutes 

 under five leading genera. 1 . Voluta, — having the spire 

 excessively short, thick, and invariably smooth ; the 

 suture of the body-whorl being generally covered with 

 a vitreous deposition or glazing, never seen in the next 

 genus. 2. Cymbiola, — having the body-whorl less ven- 

 tricose, and the spire longer ; the apex not near so thick ; 

 while, in all those species which are coronated, the whorls 

 are marked with tubercles. In both these groups, the 

 plaits are almost invariably four, — the upper ones very 

 thin and small, while the lowest is nearly double their 

 thickness. This structure of the plaits, it may be here 

 observed, belongs alone to these two typical genera. The 

 third genus is Harpula, where the plaits upon the 

 pillar are very numerous, — the upper ones remarkably 

 slender, but gradually increasing in size and thickness, 

 until the last, or the two last, which suddenly become 

 smaller : the terminal whorls of the spire, although 

 still papillary, are much more slender. The form of 

 the spire, however, undergoes a change in this group, 

 and is therefore of secondary importance. This gra- 

 dual diminution of one of the typical peculiarities of 

 the Volutince prepares us for the fourtli genus, Volii- 

 tilithes, where the apex is perfectly regulai" and acute. 



