UNIVALVE MOLLUSCA., 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 (Brug.). 
Fig. 244 —Cerithium Fig. 245.—Cerithium giganteum 
aluco. (Lamarck). 
is prolonged into a siphon. The species are all marine, and are 
carnivorous. tt 
The first family is the Cygr@ide, containing the well-known genera, 
Cyprea and Ovulum. 
