MOLLUSC A. GASTEROPODA. 161 



Murex. Shell oval or elongate, solid, spire prominent, 

 whorls convex, carrying three or more continuous longi- 

 tudinal varices, which may be spiny, foliaceous, or tuber- 

 cular. Aperture rounded, anterior canal more or less long, 

 narrow and tubular, often partly closed; no posterior 

 canal ; outer lip thick. Operculum oval, nucleus sub- 

 apical. Upper Cretaceous to present day. 



Mitra. Shell fusiform, thick. Spire elevated, summit 

 acute. Aperture narrow, elongate, notched in front. 

 Columella with oblique folds, of which the posterior are 

 the stronger ; outer lip not reflected, thickened internally. 

 No operculum. Eocene to present day. 



Voluta. Shell ovate or fusiform, solid, thick, summit 

 of spire mammilated. Last whorl very large, aperture 

 elongate, oval ; canal very short, recurved ; outer lip 

 simple, often thick, rarely reflected. Columella with ob- 

 lique folds, of which the anterior are the stronger. No 

 operculum. Upper Cretaceous to present day. 



Pleurotoma. - Shell turreted, fusiform, spire long. 

 Aperture oval; outer lip curved, provided with a deep 

 slit near the suture ; inner lip smooth. Canal long, 

 straight, narrow. Operculum horny, ovate, acute, nucleus 

 apical. Cretaceous to present day. 



Conus. Shell inversely conical, generally smooth. 

 Spire short, many-whorled. Aperture narrow, straight, 

 with parallel or sub-parallel borders; outer lip thin, 

 simple, no folds or teeth, notched at the suture. Columella 

 straight, smooth. Operculum horny, much smaller than 

 the aperture. Cretaceous to present day. 





w. p. 11 



