PTEROPODA AXD GASTROPODA. 575 



A. Holostomata, Margin of the shell-aperture entire. 

 Family CtipuloidcB. Shell limpet-shaped, with the apex sub- 

 spiral. 



Genera Pileopsis^ Hipponyx, Crepidula, Calyptrcea, Lithedaphus. 



Family TurhinidcE. In the following families the shell is spiral 

 and pyramidal, or turbinated. 



Grenera Turbo, Phasianella, Trochus, Monodonta, Delphinula, 

 Euomphahis, Stomatella, Broderipia. 

 Family NeritidcB. 



Genera NerUa, Pileolus, Neritina, Navicella. 

 Family Paludinidce. 



Genera Paludina, AmpuUaria, Valvata, Janthina. 



Family LitorinidcB. 



Genera Litorina, Solarium, Litiopa, Rissoa. 



Family Turritellidce. 



Genera Turritella, VermetuSy Scalaria. 



Family Melaniadte. 



Genera MelaniOf Paludomtis, Melanopsis, 



Family CerithiadcB. 



Genera Cerithium, Potamides, NerincEa, Struthiolaria. 



Family PyramidellidcB. 



Genera Pyramidella, Stylina, Macrocheilus. 



Family NaticidfB. 



Genera Natica, Sigaretus, Veiatina. 



B. Siphonostomata. Margin of the shell-aperture notched or 

 produced into a canal. 

 Family CyprceidcB. 



Genera, Cyprcea, Erato, Ovulum. 



Family Volutidce. 



Genera Valuta, Olivay Cymba, Mitra, Valvaria, Marginella. 



Family Conidce. 



Genera Conus, Pleurotoma. 



Family Buccinid<B. 



Genera Buceinum, Harpa, Cassis, Purpura, Ebumea, Terebra, 

 Nassa, Monoceros, Dolium. 



Family MuricidtB. 



Genera Murex, Ranella, Triton, Fasciolaria, Turbinella, Can- 

 cellaria, Pyrula, Fusus. 



Family Strombidce. 



Genera Strombus, Pteroceras, Rostellarut. 



