226 Mr C. Collier 07t Univalves. 



which seem to authorise the separation of the shell as an object 

 of Natural History, from its occupant. It may be observed, 

 in limine, that all the animals, excepting the tubiform, are 

 fixed by muscular attachment, and cannot of course quit the 

 shell. What has been reported of the cowrie and others, in 

 opposition to this, is fabulous *. 



The mantle has been represented by some authors as display- 

 ing the designs and colours of the shell ; but a much greater re- 

 semblance has been attributed than is warranted by facts. It 

 does, indeed, occasionally represent the exterior, but in a faint de- 

 gree ; and not unfrequently it has no resemblance at all. In ge- 

 neral, it is pale, excepting at the edge, or fringe, which is some- 

 times spotted, sometimes uniformly coloured. The Cyprcea viau- 

 ritania, and C. exanthema, are instances of the first of these cases. 

 In the former shell, the edge of the mantle is of a dark hue, 

 the latter has scattered yellowish spots ; and such, it may be 

 worth noting, is sometimes the case with the Argus f, and some- 

 times not. The Bulla Ovum, and Cyfrcea Talpa, are instances 

 of the second case. In the former shell, it is black, with white 

 points of a granular appearance ; in the latter greyish, and 

 raised here and there, as in the spotted shells. All the families 

 present instances of this latter case. 



The operculum is affixed to the foot. It varies in strength, 

 form, and point of attachment ; being thick, firm, leathery, py- 

 riform, affixed to the summit, and closing more or less com- 

 pletely the aperture, in the species of Strombns, Mitrex\ (except- 

 ing the fusiform), and in Buccinicm spiratum and patulum ; 

 thin, flexible, horny, circular, plane or concave, in the species of 

 Trochus, the fusiform shells of all genera, in Turbo delphinu,s\ 



• This remark is applicable to the Bulla ampulla, although its connexion, 

 like that of the operculum in the Aplysia, is by a duplication of the skin em- 

 bracing the pillar. It may be observed here, that this animal is, by its 

 structure, a species of the Aplysia, and consequently differs from all other 

 moljusca with testaceous coverings. 



+ A circumstance caused perhaps by difference of age or season. 



X It may be observed here, before proceeding further with the features, 

 that the Bulla Terebelluvi, and a species of Conus (the Figulinus, I believe), 

 are inhabited by mollusca the same in form and structure as those within 

 the shells which belong strictly to the genus Strombus. It will be unne- 

 cessary, therefore, when alluding to this family, to repeat, that such appear- 

 ances belong also to these species. 



