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distinct characters have induced Lamarck to make 

 the only species known* the type of a separate genus, 

 immediately following that of G. Monoceros; it has 

 two teeth at the base of the right side instead of 

 one, as in that genus. Shell oval, inflated, half spiral ; 

 the summit inclined obliquely on the left side; colu- 

 mella flat; aperture very ample, oblique, longitudinal, 

 with a slight notch at the base. Two teeth at the 

 lower part of the right margin. An oblong, thin, horny 

 operculum. Lamarck does not mention some other 

 peculiar characters of this shell : the small summit 

 (when seen in a perfect state) is formed of spiral whorls, 

 nearly concealed by the very widely expanded aper- 

 ture, the left side of which is greatly reflected, and 

 forms a sharp angle above it; the right lip crenatedat 

 the base. The shell is seldom seen otherwise than 

 much wormed, but the exterior presents transverse 

 grooves or slender ribs, diverging from the apex to 

 the margin, imbricated with small scales. What La- 

 marck terms the teeth differ in appearance from those 

 of the G. Monoceros, being flattened and broader, and 

 merely the continuation of two external, thickened ribs. 

 Sowerby very properly considers it nearly allied to the 

 G. Purpura. 



Concholepas Peruvianus. 

 s2 



