CONCHOLOGY. 



glowing yellow. It is under these differences of appearance that the 

 same species has been divided by some collectqrs into different 

 species, and hence it is that besides perversa we find ccerulescens, 

 virescens, citrina (or citrinus,) and aurea (or aureus,) all which varia- 

 tions in the tints or shades of colour may be very safely attributed to 

 accidental causes producing a discolouration of the natural complexion 

 of the shell, which is of a yellow colour, more or less vivid, or 

 varying from a pale citron hue to a fine yellow. 



Perhaps we ought to mention that there is some slight difference 

 occasionally observable in the greater or less development of the lip 

 and margin, and which in the region of the umbilicus sometimes ex- 

 tends so far as partially to cover it. There are variations dependent 

 only upon its state of growth, the lip being thinner in the younger 

 shell and becoming gradually more enlarged as it advances towards 

 the adult state. The records of science are not without examples 

 even of such progressive appearances being considered as generical 

 indications, and we cannot therefore be surprised to find it regarded by 

 other more cautious naturalists as probably nothing more than a 

 specifical distinction. 



Besides these shells, which are entirely yellow, there are others 

 which exhibit a single longitudinal brown streak, or band, and some- 

 times two, remotely distant from each other, across the first or second 

 volution. 



The third kind or variety are those which are striped or spotted. 

 Those, like the preceding, are reversed, or otherwise, for the spiral 

 wreath is not uniformly in the same direction ; generally they are 



