CONCHOLOGY. 
Includes Turbo unidentatus and others. 
6. TURBINACIDE. 
Pillar without plaits—shell conic or elongated ; 
aperture roundish or oblong, never expanded, with 
the lips either united or separated. 
73. Tornus. Sheli orbicular, depressed: aper- 
ure oval or roundish; pillar none. Operculum 
horny. 
Includes Helix subcarinata, 
74, Trochus. Shell conic: aperture angular, 
with the lips disunited: pillar arched, a little 
prominent at the base. Operculum horny, 
Includes the Trochus family, 
75. Turbo. Shell solid, conoid: aperture 
rounded, with the lips disunited. Pillar arched, 
flattened, imperforate, not truncate at the base. 
Operculum horny. 
Includes Turbo litoreus, Nerita litoralis, &c. 
76. Lacuna. Shell thin, conoid or somewhat 
globular, clothed with an epidermis: aperture 
roundish-oval, with the lips disunited. Pillar 
flattened, with a longitudmal groove which 
terminates at the upper end in an umbilicus, © 
Operculum horny. 
Inciudes Helix Lacuna, Turbo vinctus, Nerita 
pallidula, &c. 
77. Planaxis. Shell solid, conic-oval : aperture 
oval; pillar depressed at the base and obliquely 
truncate, separated from the outer lip by a narrow 
