snails and slugs

The most diverse class; found in the widest range of habitats - marine, freshwater, terrestrial
a) have 1, usually coiled shell
b) have a large, creeping foot; most move using muscular waves
c) united by a bizarre developmental process; torsion (twisting of posterior end over head; adaptive significance remains a puzzle)
d) primitively were rasping grazers, but feeding ecology is diverse
e) divided into 3 subclasses: - Prosobranchia (marine snails) - Opisthobranchia (sea slugs) - Pulmonata (land snails and slugs) 

     
   

chitons

Marine grazers on hard bottom
a) an unusual 8-plated shell is surrounded by an extensive 'girdle'
b) 8 pairs of pedal retractor muscles connect the foot to the plates
c) multiple ctenidia lie in lateral grooves of the mantle cavity

the 'tusk shells'

a) curious tubular shell; originates as shells in larva that fuse
b) head is reduced, but have a well-developed foot for burrowing
c) lack ctenidia but possess a radula
d) are micro-predators; they capture foraminifera with captacula

clams, oysters, scallops

2nd most diverse class
a) body plan is highly modified for a burrowing, filter-feeding mode of life (body is laterally compressed and wholly enclosed inside mantle and shell; head and radula are absent)
b) shell composed of 2 valves joined by a flexible ligament; mantle edge is fused to the shell margin and linked to adductor muscles
c) foot is highly modified for burrowing (except attached species); burrowing involves both shell and foot

     
   

nautilus, squids, octopus

3rd major class
a) includes most highly advanced, largest and fastest invertebrates; body plan modified for pelagic life
b) exclusively marine carnivores (eat fish, crustaceans, molluscs)
c) shell is reduced or absent; head and foot form tentacles and siphon
d) extinct forms had well-developed shells with gas-filled chambers
e) very sophisticated eyes and balance organs (statocysts)
f) 1 or 2 pair of ctenidia lacking cilia
g) have a true 'closed' circulatory system lined by endothelium
h) mantle is muscular and mantle v\cavity large; jet-propulsion is achieved via antagonism of circular and radial mantle muscles
i) three subclasses; Nautiloidea - 1 living genus; Ammonoidea - extinct; Coleoidea (Or. Decapoda, Or. Octopoda)

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Links about Malacology:

American Malacological Society - An organization dedicated to the study and preservation of mollusks.

Malacological Society of Australasia - Promotes the study, conservation, and appreciation of molluscs in the region. Information about the society, publications, meetings, and research support.

Malacology in Latvia - Directory of Latvian malacologists, checklist of Latvian species, bibliography, and other research information about Latvian malacology.

Man and Mollusc - An introduction to mollusks, with emphasis on their relationship with man.

Mollusc Molecular News - Database of resources and research on mollusc RNA and DNA, including researchers, publications, PCR primers, and DNA amplification protocols.

Molluscan Journals - Authors' instructions from journals. Supplied by Mollia.

Peter Solymos's Research - Hungarian malacologist's personal site with list of recent publications related to land snails.

Soosiana Hungarian Malacological Journal - Tables of contents and general information about the journal. In Hungarian and English.

Vita Marina and Spirula - Magazine and newsletter for malacology and conchology. 

Links about Gastropoda:

ABMAP: The Abalone Mapping Project - Documents and illustrates the current geographic distribution of abalone (Gastropoda: Vetigastropoda: Haliotidae: Haliotis) world-wide.

Class Gastropoda - Overview of gastropod classification from the Animal Diversity Web.

Eurasia Shells - Large collection of gastropod specimen images (over 900 species) from the Philippines, rarely represented in the literature.

Freshwater Snails Of Florida - Contains an online version of The Freshwater Snails of Florida, a manual for identification, prepared by Fred G. Thompson.

Gastropoda of Montana - Overview of biology and taxonomy; species list for Montana.

Gastropods - Information on gastropods from an aquarist's viewpoint. Includes pages on specific orders of gastropods, as well as a general gastropod FAQ.

Hardy's Internet Guide to Marine Gastropods - A virtual encyclopedia of sea snails. The catalog is organized taxonomically, and contains pictures, common and scientific names, and basic taxonomic information for a large number of species.

Living Fossils of the Deep - Expedition to the deep sea of the Bahamas to explore the world of slitsnails. From the Smithsonian Institutes National Museum of Natural History.

NMITA Gastropod taxonomic list - The list provides a current systematic framework and summary of the taxonomic diversity of Panama Paleontology Project (PPP) mollusc collections collected, curated and identified from project inception till October 2000.

The Living World of Snails and Slugs - General information about the biology of gastropods as well as about the relation between snails and man.