450 



flrong fpecific dlRinclions. " Pumorbis tejia Jlavofvfca. 

 Jub-carinata, fupra concava, fubtus plana" 



It is fomewhat extraordinary that Schroeter fhould 

 have given a figure of this (hell, and a very exa6t de- 

 fcription, with the title of, " Coriiii ammonis 6 gyris ro- 

 tundis circuvif crip turn," making a comparative didinfti- 

 on between it and the Vortex, and yet had not difcovered 

 it to be the Spirorbis, as is evident by his defcribing 

 that Iheil in another place. 



This fpecies never grows fo large as the Vortex, but 

 both are alike finely ilriated, or wrinkled, acrofs the vo- 

 lutions in an oblique dire6lion; and the number of 

 ■whirls are equal in Ihells of the fame fize. 



The Spirorbis is never carlnated like the Vortex, con- 

 fequently the aperture is not angulated at the exterior 

 margin, as in that ihell : this too has the volutions raifed, 

 and rounded equally on both fides, and a deep feparating 

 line; the other has the volutions on the under fide quite 

 flat, and the line of feparation not fo deep ; befides 

 •which, this is not quite fo thin or deprefied as the Vor- 

 tex, when compared with that fhell of the fame fize. 



Thefe difl:inguifhing charafters are invariable, and by 

 which both fpecies inay be readily known from each other. 



This has generally been defcribed as the more rare, 

 but we believe it is equally plentiful in England, at leafl; 



it 



