442 



to fuch authority : but as we have frequently found it 

 with the paludofa, and often times fo httle ftriated as 

 fcarce to be feparated, think it but right to prepare 

 others for fo nice a difcrimination. 



Mr. LiGHTFOOT has given a very good figure of this 

 fhell in the Philofophical TranfaBions for 1786", confi- 

 dering it a nondefcript fpecies. Whether he was ac- 

 quainted with the H. paludofa of Da Costa, which 

 is figured in Walker's minuta rariora is uncertain; 

 but probably not, or he would have mentioned the great 

 fimilitude between thefe. He particularly fays, the vo- 

 lutions are tranfverfely furroundedwith numerous fharp- 

 edged membranaceous rings, which are very fragile 

 and deciduous. 



If it is really diftinft from the H. paludofa, we fear no 

 permanent, fpecific charafter of diflinftion, will ever be 

 fixed ; for every gradation is to be feen, from the ftrong- 

 eft flriated, to tliofe deltitute of any fuch mark: both 

 are equally pellucid white, when divefted of their brown 

 epidermis, in a living or recent ftate ; and opaque in 

 old dead fliells. 



In fome the ridges or ftrix are much elevated, and 

 mollly membranaceous, but in fuch (Irong marked fpe- 

 cimens the bafe of thefe ftriee are permanent or teftace- 

 ous, not to be deftroyed by rubbing off the epidermis ; 

 whereas, in others that appear flriated when frefh, are 



wholly 



