CERITHIUM. 191 



the tentacula being widely extended, and used as feelers." 

 We have always found it very sluggish and unwilling to 

 display itself when captured. 



This curious mollusk is generally distributed around 

 the British shores, so much so, that to enumerate loca- 

 lities would be superfluous It ranges from a depth of 

 four to as much as one hundred fathoms, and has been 

 dredged alive in many intermediate depths. It affects 

 gravelly bottoms. 



It inhabits all the coasts of Europe, and is found 

 fossil in both red and coralline crags, and in pleistocene 

 strata. 



CERITHIUM, Adanson. 



Shell spiral, turriculated, with an elongated many-whorled 

 spire, usually solid, surface variously ornamented with 

 ribs, grooves, and tubercles, rarely smooth ; aperture sub- 

 quadrate, terminating below in a more or less deve- 

 loped, short, usually recurved canal. Operculum corneous, 

 spiral. 



Animal with a thick muzzle-shaped head bearing two 

 subulate tentacles with eyes on prominent bulgings near 

 their external bases ; no neck-lobes or lateral filaments ; 

 mantle wdth a short siphonal fold ; foot sub-triangular, 

 rather short. 



This is a large genus, including between one and two 

 hundred species, some of which have been set apart under 

 other generic appellations, on account of slight modifica- 

 tions of the canal of the shell, and a supjiosed corre- 

 spondence between these peculiarities and the habits of 

 the animal. All our British examples are truly marine, 

 and are small and inconspicuous. In tropical seas, and 



