CLASS II. GASTEROPOILA (q.v.). These animals never inhabit a bivalve shell. Many are naked, but the majority are provided with a univalve, sometimes with a multivalve shell. The gasteropods are divided into two primary sections, pulinowfera and branchi fera, according as their respiratory organs are formed for breathing in free air or in water.
SEcTiort A. BRANCHIPERA. In this section the respiration is aquatic, by walls of the mantle cavity, or by gills. Divided into three orders.
Order I. ProsobranclaVta (Pectinibranchiata). Branchise pectinated or and situated in advance of the heart, whenCe the name.
Section 1. Siphonoston•ata (q.v.). Margin of shell notched or produced into a canal. Comprises six families.
Family 1. Strombidee (v.).
Family 2. Ifuricichr. bee MUREX, PURPLE COLORS, and Fusus. • Family 3. Buccinicke. See PURPURA, HELMET SHELL, and WHELK.
Family 4. Coitic/ce. See CONE SHELL.
Family 5. Volulace (q.v.). • Family 6. Cypraiebv. See COWRY.
Section 2. Ilolostomata. Margin of shell seldom notched or produced into a canal. Family 7. Naticidee.
Family 8. Pyramidellidce. See CIIEMNITZIA.
114mily 9. Cerithiadee.
Family 10. Melaniadce.
Family 11. Turretellido3 (q.v.).
Family 12. Littorinidce, periwinkle (q.v.).
Family 13. Paludinidce, river snails, ampullaria, and paludina, the latter well known.
Family 14. Neriticke. Globose shell; long slender tentacles; mostly marine, and belonging to the tropics; one British species.
Family 15. Turbinida (q.v.). Top shells. See PIIEASANT SHELL and TROCIIID2E.
Family 16. Haloitida, ear-shells (q.v.). Shell spiral, ear-shaped. See HAmoTis and IANTHINA.
Family 17. FissureWee (q.v.).
Family 18. Ciayptreeidai. See CALYPTRAA.
Family 19. Patellidce. See LIMPET.
Family 2-0. Dentalidee. See DANTALIUM.
Family 21. Chiloniche. See CHITON.
Order IL Opisthobranchiata. Branchim placed toward the rear of the body, whence the name.
Section 1. Tectibranchiata. Branchim covered by a shell or mantle, a shell in most; sexes united.
Family 1. Tornalellidce. Cretaceous, principally.
Fami/y 2. Bubble shells. See Bum.A.
Family 3. Aplysiadm. Shell absent or rudimentary, and concealed by the mantle; animal slug-like (aplysia).
10mily 4. Pleurobranchidce. Shell covers only the back of the animal. That of one species is known as the Chinese umbrella.
Romig Phyllidiacke. Shell absent.
Section, 2. Nudibranchiata (q.v.). Animals destitute of a shell in the adult condition. Branehire external, on the back or sides of the body.
Family 6. Doridce. Sea lemons. See Donis.
Family 7. Tritoniadce. Nearly allied- to the preceding.
Family 8. 4]olidee. See GLAUCUS.
Family 9. Phyllirhoidce.
Family 10. Elysicuice, elysia, actmonia.
Order III. Nucleobranehiata (q.v.) or Heteropoda. Shell present or absent; animal free in the open sea, with a tin-like tail or flattened ventral fin.
Antily 1. See FIROLA and CARINARIA.
Family 2. Atlantidce. See BELLEROPHON. •