One of the classes of Mollusca, of great extent. It includes most of the marine spiral shells, and the land and fresh-water snails. They generally creep by means of a flat, muscular disk, or foot, on the ventral side of the body. The head usually bears one or two pairs of tentacles. See Mollusca
. [1913 Webster
" The Gastropoda are divided into three subclasses; viz.: (a) The Streptoneura or Dioecia, including the Pectinibranchiata, Rhipidoglossa, Docoglossa, and Heteropoda. (b) The Euthyneura, including the Pulmonata and Opisthobranchia. (c) The Amphineura, including the Polyplacophora and Aplacophora."