256 CERITHIID^. 



This family has some relations to Twritellidce and 

 ScalariidcB ; but^ in the present state of our knowledge, 

 it is impossible to make a complete system of arrange- 

 ment for the Mollusca, or one which will fit every group 

 into its proper place. 



Genus CERI'THIUM* Adanson. PI. IV. f. 4. 



Body slender : head broad and short : [mentum distinct, 

 nearly free in front, actively vibrating : (Loven)] foot notched 

 or bilobed in front : opercular lobe simple. 



Shell as described in the account of the family. 



The difference between a true canal, indicated by an 

 outside notch, and a mere groove inside the base of the 

 shell was not unobserved by Linne, who says of his 

 Trochus perversus [C. perversum), ^*^ columella basi pro- 

 minula, at non in canalem evidentem." Deshayes sepa- 

 rated this and other sinistrorsal species as a distinct 

 genus [Triforis), because the mouth is apparently divided 

 into three orifices. Their structure, however, is essen- 

 tially the same as that of the smaller dextrorsal species, 

 which Leach called Bit Hum. Colonna first applied the 

 name Cerithium to this kind of shell ; Prevost spelt it 

 (perhaps more corectly) Ceritium. There is no end of 

 synonyms ; and if I were to give all in every genus and 

 species which I describe, this work would be unneces- 

 sarily swollen to twice its present size. 



1. Cerithium me'tulaI, Loven. 



C. metula, Lov. Ind. Moll. Scand. p. 23 ; F. & H. iii. p. 198, pi. xci. 

 f.3,4. 



Body thick and muscular, milk-white : pallial fold distinct : 



* Probably from Kcpdrtor, a small horn ; hence KepaTivrj, buccina. 

 t An obelisk. 



