UNIVALVE MOLLUSCA. 



439 



imperforate, the animal of which has sometimes a homy operculum, 

 and is furnished with a retractile proboscis; the margin of the mantle 



Fig. 243. — Cerith'tim 

 fasciatum (Brug.)- 



Fig. 244 — Cerithium 

 aluco. 



Kig. 245. — Cerithium giganteum 

 (Lamarck). 



is prolonged into a siphon. The species are all marine, and are 

 carnivorous. 



The first family is the Cyprmdce, containing the well-known genera, 

 Cyprcea and Ovulum. 



