Section Tectibranchiata—Gills covered by shell or mantle.
Order Pulmonifera—Lung-breathers. Terrestrial.
Order Prosobranchiata.
Section Holostomata—Aperture of shell entire (sea snails).
Families—Chitonidæ, Dentaliadæ, Patellidæ, Calyptræidæ, Fissurellidæ, Haliotidæ, Turbinidæ, Littorinidæ, Turritellidæ, Cerithiadæ, Pyramidellidæ, Naticidæ, &c.
Section Siphonostomata—Possess a true siphon. Carnivorous.
Families—Cypræidæ, Conidæ, Buccinidæ, Muricidæ, &c.
Class CEPHALOPODA—Sucker-bearing arms round the mouth.
Order Dibranchiata—Two gills.
Section Octopoda—Eight arms.