48 



might with less hesitation point out which of those at 

 present called Cerites ought to be removed to Potamides, 

 but the two genera are as likely to be mixed as the 

 Oysters, Cyclades, Malanopses, Ancillae, &c. that ac- 

 company them, in beds, between the two fresh water 

 strata, on the Isle of Wight, or above the white Sand 

 at Charlton, &c. 



If the characters above mentioned could be relied 

 upon, which we fear is not strictly the case as far as 

 concerns the form of the mouth, the following species, 

 published at tab. 147, should be arranged as Potamides, 

 Cer. funlculatum, Cer. intermedium, Cer. dubium, and 

 Cer. Melanioides ; the two last have the best claim to 

 removal ; perhaps Cer. funatum, tab. 127, ought also to 

 be removed ; it appears to have a small groove or canal 

 at the junction of the right lip with the spire, although 

 hardly enough to be considered of importance ; indeed 

 such a groove is observable in some of the recent Po- 

 tamides. 



POTAMIDES rigidiis. 

 TAB. CCCXXXVIIL 



Spec. Char. Subulato-conical, nearly smooth; 

 lower whorls surrounded by a keel near 

 their upper parts. 



Syn. Buccinum rip;idnra, Drander, 43. 



^OME obscure furrows indicating the lines of growth are 

 observable regularly covering the otherways smooth sur- 

 face of this shell : from the curvature of these lines, and 



