158 C O N C H O L O G Y. 



inch long, and a quarter of an inch over : and 

 befides their great difference in fize, they 

 no wife tally in other parti cuhu's with the 

 larger, fo as to be imagined young ones 

 of the fame ipecies. 



Breynius, who firil: formed this genus in 

 his w^ork de Polythalamiis, propoles nine 

 kinds* and I have obferved fome others 

 not mentioned by him. 



I would divide this genus into two fec- 

 tions, viz. ift. thofe that have the fiphun- 

 culus placed on or near the edge; and 2dly, 

 thofe that have it central, or near the 

 center. 



It IS proper to obferve, that thefe foffils 

 are always cafts of ftone or replacements 

 of fparry matter. I have however feen, 

 though extreme rarely, flight fragments of 

 the {hell on them, which fragments were 

 whitifli and very thin. 



Genus 



