.322 



HELICID^E. 



sess a remarkable similarity of size, color, and general 

 aspect ; and the white, lamelliform tooth of the aperture 

 serves at once to distinguish them from every other spe- 

 cies. The normal number of teeth, or that number 

 which is most commonly observed in adult individuals is 

 certainly/owr; but, in addition to those described, there 

 is sometimes a small tubercle, or diminutive tooth, very 

 near the junction of the lip and body whorl, and more 

 rarely another of the same description, at the base of the 

 aperture, near the umbilical tooth. If those only are to 

 be considered fully mature which possess all the teeth, 

 then the species may be characterized as having six teeth 

 in the aperture ; but as one of them is nearly always, and 

 another generally, wanting, the description here given is 

 correct. The margin of the lip is sometimes continuous 

 entirely around the aperture. 



