PTEROPODA AND GASTROPODA. 575 



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

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

 spiral. 



Genera Pileopsis, Ilipponyx^ Crepidula, CalyptrcBa, Lithedaphus. 



Family TurhinidcB. In the following families the shell is spiral 

 and pyramidal, or turbinated. 



Genera Turbo, Phasianella, Trochus, Monodonta, Delpliiimla, 

 Euomphalus, Stomatella, J3roderipia. 

 Family NeritidcB. 



Genera Nerita, Pileolus, Neriti?ia, Navicella. 

 Family Paludinidce. 



Genera Paludina, Ampullariaf Valvata, Janthina. 



Family Litorinidce. 



Genera Litorina, Solarium, Litiopa, Rissoa. 



Family TurritellidcE, 



Genera Turritellay Vermetua, Scalaria. 

 Family MelaniadcB. 



Genera Melania, Paludomus, Melanopsis. 



Family CerithiadcE. 



Genera Cerithium, PotamideSy Nerin^a, Struthiolaria, 



Family Pyramidellidce. 



Genera Pyramidella, StylinOy Macrocheilus. 



Family Naticidce. 



Genera Naticay Sigaretus, Velatina, 



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

 produced into a canal. 

 Family Cyprceidce. 



Genera, Cyprcea, Erato, Ovulum. 



Family VolutidcB. 



Genera Voluta, Oliva, Cymba, Mitra, Valvaria, Maryinella. 



Family Conidce. 



Genera Conus. Pleurofoma. 



Family BuccinidcB, 



Genera Buccinumy Harpa, Cassis, Piirpura, Eburneay Terebra, 

 Nassay Monoceros, Dolium. 



Family Muricidce. 



Genera Murex, Ranella, Tritoiiy FasciolariUy Turbinellay Can- 

 cellariay Pyrulay Fusus. 



Family Strombidce. 



Genera StrombuSy Pteroceras, Rostellaria. 



