'^ 



of the genus Marginella. 441 



tance from their termination. The belly of the shell is 

 wholly covered with a brilliant, white callosity, formed 

 by the deposit of vitreous matter. 



Length fourteen-twentieths, breadth nine-twentieths of 

 an inch. 



Inhabits the southern coasts of the Gulf of Mexico. 

 In the Cabinet of the Boston Society of Natural History, 

 that of D. H. Storer, M. D., and my own collection. 



The shell bearing most resemblance to it is the M. 

 bivaricdsa ; but in addition to the spire of that species 

 being much more prominent, the folds on the columella, 

 have all nearly the same direction, the margin is double 

 and its edges rounded ; whereas, in this, the two upper 

 folds are nearly transverse, the two lower verj^ oblique, 



^ I 



and the edges of the margin very sharply defined. It is 

 also much broader in proportion to its length than the M. 

 hivaricosa. The most unpractised eye could not fail to 

 detect a difference instantaneously, between the two shells. 

 In both the specimens in my possession, the characters 

 above mentioned are uniform. 



It is far from my intention to Indulge in the too preva- 

 lent system of constituting new species from mere varie- 

 ties of a shell ; but while we have such authority as 

 Lamarck and Kienerfor considering the M.faha and M. 

 bijasciata, the M. formicula and M. muscdria^ the M. 

 glabella and M. aurantia as being each distinct species ; 

 where the closest scrutiny can detect no other differences 

 than those of size and coloration ; the shell under con- 

 sideration must be acknowledged to possess far stronger 

 claims to a name of its own. 



It can hardly be doubted, that had any of the Euro- 

 pean naturalists met with it, they would have designated 



^ 



s I 



It as a new species ; and after the fiat 



VOL. I. PART IV. 57 



pproba 



