94 
MUREX. 
The very peculiar form of the aperture in this 
genus is a strong and never-failing distinctive fea- 
ture. This is oblong-oval, or perfectly oval, seldom 
ovate, and does not gradually contract into a canal, 
but abruptly opens into it at the same or nearly the 
same width which it continues to retain through- 
out the whole length of the beak. Even in the 
division which is destitute of an exserted beak, the 
same contour is no less observable. The strais:ht- 
ness of the rostrum is a much more questionable 
mark, than the outline of the aperture, which when 
once understood cannot easily be mistaken. 
The last section which has been added to those 
in the Linnsean arrangement of this genus, appears 
to be absolutely indispensable. A plaited columella 
having been assumed as the generic character of 
Voluta, it can only be with some strong reason 
that shells so furnished are admitted into other 
genera : such a reason is however found for the 
plaited Murices in the structure of the mouth, 
which at once identifies them, notwithstanding any 
other claim. But they surely deserve to be set 
apart as a distinct branch of the family : for generic 
characters, when they lose their validity as such. 
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