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lip : the plait upon the columella is independaut of the 

 inner edge of the beak, which is obtuse. It dill'ers from 

 P. Lamarckii of Brochant in having a longer beak, and 

 this plait upon the columella. 



From the same formation as the last ; collected by 

 Mr. G. B. Sowerby at Headon Hill. 



POTAMIDES? plicatns. 

 TAB. CCCXh.— Fig. 2. 



Spec. Char. Subulato-conical, or subcylindrical ; whorls 

 longitudinally plaited, transversely sulcated and 

 striated ; sulci 3 or 4 ; base convex ; lip crenulated. 



Syn. Cerithium plicatum. Lamarck Env.de PariSy 8i. 



The crossing of the sulci over the plaits form arched 

 rows of obtuse tubercles ; the plaits are deepest upon the 

 upper part of each whorl, so that the base appears less 

 regularly tuberculated ; the beak is rather contracted, 

 and there is moreover a small canal at the upper angle 

 of the otherways round aperture. 



Found in the upper marine formation, upon the Isle 

 of Wight, by Prof. Sedgwick. 



POTAMIDES duplex. 



TAB. CCCXL.— Fig. 3. 



Spec. Char. Subulato-conical, with two rows of tuber- 

 cles upon the upper, and three upon the lower whorls ; 

 upper rows of tubercles largest ; sides of the whorls 

 flat ; base flat, with two carinas near its edge ; beak 

 short, inner edge rising upon the columella. 



This differs from P. cinctus in having only two rows of 

 granules upon the upper whorls, and in their being so 



