82 



Figure. 



Ricinula iodostoma. PL 7. Fig. 32. Front view of the shell, showing 

 the aperture and plait-like denticles of the columella and inner lip. 



Genus 22. CASSIS, Lamarck. 



Animal ; disc oval, rather thin, flattened, carrying a small crescent- 

 shaped operculum at the posterior end; head stout, obtuse, pro- 

 longed into two slender tentacles, with the eyes on the outer side 

 near the base ; respiratory siphon large and elongated, pro- 

 boscis short, cylindrical. 

 Shell ; ovate or triangularly ovate, terminating at the base with a 

 short peculiarly recurved and ascending canal; spire short, and 

 often crossed at intervals with varices ; last whorl of the shell 

 inflated, sometimes remotely strengthened with varices ; aperture 

 large, though often narrow ; columellar lip frequently wrinkled 

 or granulated, outer lip thickened, reflected and more or less 

 toothed. 



The Cassides or Helmets are a strong, muscular, but inactive group of 

 mollusks, whose shell is mainly distinguished by its solid or inflated growth 

 and short spire, and by the abrupt ascending recurvature of the canal, 

 through which the siphon for conveying the water to the breathing organs 

 passes, and is of more than ordinary dimensions. The head is stout and 

 fleshy, and prolonged into the tentacles after the manner of Purpura or 

 Buccinum, the eyes being situated on the outer surface near the base ; it 

 appears, however, from the observations of M. Deshayes, that in the Cassis 

 sulcosa they are surmounted on a short pedicle. The calcifying properties 

 of this genus are somewhat vigorously exercised, the mantle which lines the 



