240 CERITIIIOPSID^. 



Mantle not reflected, furnished with a rudimentary si- 

 phonal fold. Foot oblong, subquadrate in front, where 

 it is furnished superiorly with a mentum, grooved for half 

 its length below, the groove terminating in a perfora- 

 tion ; operculigerous lobe well developed. 



The head is compressed and vertically cloven in front, 

 and the tips of the tentacles are obtuse or very slightly 

 clavate ; the eyes are placed rather close together towards 

 the centre of the base of the tentacles. 



Genus CERITHIOPSIS, Forbes and Hanley. 



Operculum corneous, of concentric elements, nucleus 

 terminal. 



Shell turreted, many-whorled, dextral, granulated ; 

 aperture subrotund ; inner lip broadly reflected ; outer 

 lip acute, arcuated and produced anteriorly ; aperture an- 

 teriorly sinuated ; canal short. 



Ex. C. tubercularis, Montagu, pi. 25, fig. 5. Oper- 

 culum, C. tubercularis, fig. 5, a. Shell, C. tubercularis, 

 fig. 5, h. 



The characters of this genus are so peculiar as to war- 

 rant its forming the type of a distinct family ; the nature 

 of the lingual dentition induced the learned authors of 

 the " British Mollusca " to place it with Canccllaria and 

 Tricholropis, accompanied by the remark that it probably 

 has relations with Terehra. 



Species of Cerithiopsis. 



assimilata, C. B. Adams. Emersouii, C. B. Adams. 



clatbrata, A, Adams. gemmulosa, G. B. Adams. 



