UNIVALVE MOLLUSC A. 



439 



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

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



Fig. 243. Cerithium 

 fasciatum (13 rug.). 



Fig. 244 Cerithium 

 aluco. 



Fig. 245. Cerithium giganteum 

 (Lamarck). 



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

 carnivorous. 



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

 Cyprcza and Ovulum. 



