CEMTHIOPSID.£. 265 



Family XXVI. CEKITHIOFSID^E, Gray. 

 Contains only the 



Genns CEBITHIOP'SIS*, Forbes and Hanley. 



PL IV. f. 5. 



Body spiral, elongated: mantle plain- edged : pallial tube 

 lining the canal at the base of the shell, but not protruded 

 beyond it: head short and broad, furnished with a retractile 

 proboscis : tentacles cylindrical : eyes placed on bulgings in 

 front of the tentacles, at their base : foot lanceolate, byssiferous : 

 opercular lobe simple. [Teeth 3.1.3; central large, bifid ; 

 lateral linear. (Alder.)] 



Shell more or less cylindrical and slender, closely tuber- 

 culated or beaded, never varicose, nor umbilicate : spire taper- 

 ing to an abrupt but elongated point : ivhorls numerous, the 

 earliest very slender in proportion to the rest : suture narrow, 

 excavated : mouth small : canal extremely short, truncated, 

 and straight : operculum horny, ear-shaped, having an incom- 

 plete spire ; nucleus nearly terminal, at the inner base of the 

 mouth. 



The Siphonobranchiata here commence. The shell 

 has a distinct, although exceedingly short canal, instead 

 of a mere groove, as in Trichotropis and Cerithium ; the 

 base of Cerithiopsis is truncated, and notched outside, 

 while in the other genera the base is entire. The canal 

 in the present genus and its allies is a semitubular 

 sheath, to receive the branchial fold of the mantle. 

 Montagu pointed out the difference between Cerithium 

 reticulatum and Cerithiopsis tubercularis in nearly simi- 

 lar terms. Woodward made Cerithiopsis a subgenus of 

 Cerithium ; Clark went further, and merged Cerithiopsis 

 in Murex. Perhaps the separation of Cerithium and 

 Cerithiopsis into two families may be an equally extreme 

 mode of classification. The present genus contains 



* Having the aspect of Cerithium. 

 VOL. IV. N 



