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forming a judgment from external appearances only. 
There are I find many species that might be taken for 
yarieties, as they gradually pass through different degrees 
of obliquity. This appears to be the species Mr. Parkinson 
thinks might, if not otherwise designated, be called glabra; 
I am afraid however that there are still more glabrous ones 
to abtain the title. The line of the hinge is, as he observes, 
finely crenulated, as well as three transverse teeth which 
terminate the hinge at each end: so are some of the other 
species of this Genus, and possibly it ought to form part of 
the Generic Character, but may often be imperceptible 
from being worn, as I have it tolerably distinct in that 
Mr. P. thinks might be denominated C. decussata.. 
