204 NATICIDiR. 



where it is furnished with a fold which covers the head and 

 tentacles ; operculigerous lobe very ample, reflexed upon 

 and partially concealing the sides and back of the shell. 



Operculum distinct, spiral, few-whorled. 



Shell spiral, usually smooth or polished, more or less 

 globular; aperture semilunar, sometimes very large. 



The existence of a large operculigerous lobe is a 

 remarkable feature in this family, and serves, at once, 

 to distinguish it ; in the polished Mmnma it nearly 

 covers, and in Catitms is extended quite across, the 

 shell. The size of the operculum in this group seems 

 not to depend upon that of the mouth of the shell, being- 

 most developed in those genera which have a contracted 

 aperture, and smallest in those where the mouth is wide ; 

 thus, in Catinus it is horny and rudimentary ; in Ruma 

 horny, but large; and in Natica ample and calcareous. 

 The eggs of the Naticidce are agglutinated into broad, 

 subspiral bands, very slightly attached, and resting on 

 the sands. These animals are carnivorous and very pre- 

 daceous, feeding on the smaller bivalves, in which they 

 bore circular holes to extract the flesh. 



Genus NATICA, Adanson. 



Animal entirely retractile within the shell. 



Operculum horny, with a calcareous outer layer. 



Shell subglobose ; spire rather elevated ; aperture semi- 

 lunar; columella adherent to, and spirally contorted in, 

 the umbilicus; apex more or less dilated and truncate, 

 more rarely convex or rounded. 



Si/n. Naticus, Montf. Lunatus, Humph. Nacca, 

 Risso. Cochlis, Bolt. Naticarius, Diim. 



