122 



GASTEOPODA. 



Turritella (Lamk.). Shell lengthened, many- 

 whorled, spirally ridged ; aperture rounded ; lip 

 thin ; operculum horny, many-whorled, fringed. 



T. communis. Fig. 186; n.s. 



183 



184 



185 



FAMILY X. 



Shell spiral, lengthened, many-whorled ; aper- 

 ture channelled in front, and indistinctly behind ; 

 lip generally expanded; operculum horny, gene- 

 rally spiral. Animal with a short muzzle ; tentacles 

 distant, slender ; eyes on short stalks ; mantle 

 with a rudimentary siphon or fold. 



Aporrfiais (Aldrov.). Shell lengthened, pointed ; 

 whorls knobbed; aperture narrow; outer lip be- 

 coming expanded and fingered with age ; oper- 

 culum plaited, pointed. 



A. pes-pelicani. Fig. 187 ; n. s. 

 pes-carbonis. 



