46 



fame, but upon critical examination by comparifon, tbe dif- 

 tinftion is evident, as well in its contour as in the 

 jftru6lure of the hinge, and Hill iriore obvious by the 

 crenulce on the margin ; a circumftance alone fufficient 

 for fpecific diftin^lion were all others wanting: a cha- 

 ratler invariable, and by far more fixed and determi- 

 nate than any to be found in our frefli Avater Myce and 

 Myiilli, which are moflly deftitute of any permanent fpecific 

 diftinclion, andof courlb arc multiplied and reduced at the 

 caprice of the conchologift ; a circumftance we are all liable 

 to when obvioufly fixed cliaraclers are wanting, and wliere 

 gradation fo llrongly tends to unite them. In the prefent 

 fubjedl, however habit might accord in other refpe61:s witii 

 V. Scoiica, the conftru6lion of the margin mufi; be confidered 

 as inviolable -, no common fliell, whofe character is to pofi'efs 

 a plain margin, is ever found with a crenulated one, nor 

 vice veifd. This obvious mark of diftinftion is equally as 

 eflential in difcriminating between Vejiusfa/cataandcomprejfa. 



Lactea, Venus Lactea, Don. Br. Shells, v. t. 149 — Lin. Trans, viii. p. '9. 



Shell lentiform, fomewhat compreiled, with thick, ele- 

 vated, obtufe, concentric y?/7>, and fiightly truncated an- 

 teriorly. 



Thefe are the f}}ecific characlers given by the author of 

 the Britj/Ij Shells, who offers this as a new Brilijh fjiccies. 



It is likened to Venus horealis, (our Tellina radula) but th.e 



autlior 



