Freshwater Molluscan Shells

Gastropoda (Snails)

Neritinidae: Thick walled colorful shells with shelly operculum, mostly tropical, related to the marine
Ampullariidae: Large "apple snails" of the tropics worldwide, generally smooth globose shells, thin
    and strong.

Viviparidae: "mystery snails", usually with circular or oval aperture, generally smooth shells,
    thin but strong, conspicuous whorls.

Valvatidae: Small white snails, widely umbilicate.
Other freshwater snails: A few species from generally marine families.
Pleuroceridae and other Cerithioidian families: Thick-walled shells, often high-spired,
    may have sculpture and color, or with color bands.
North America, Africa, Asia, South America.
Thiaridae: Similar to the Pleuroceridae, mainly tropical.
Melanopsidae: Similar to the Pleuroceridae but more fusiform; Mediterranean region, also New
    Zealand, New Caledonia.

Rissoacea: A great many species of mostly small to tiny operculate snails, world wide. Diverse in
Freshwater pulmonate snails: Thin-walled shells, worldwide, usually weakly colored, may be
    dextral (
    sinistral (
Physidae), or
    planispiral (
Planorbidae), and may be restricted to certain geographic locations such as
    temperate South America (
    or New zealand (
Freshwater limpets: Thin, small, saucer or cap-shaped shells, not closely related to marine limpets.

Gastropod family tree showing relationships between the major freshwater lineages.
This is a more traditional approach to classification. Recent work suggests, for instance, that the Archaeogastropoda
is an artificial grouping, the Neritinidae belong in their own order and superorder, and also that the Viviparidae and
Ampulariidae are separate lineages, both of which should connect at the base of the Caenogastropod branch.
Furthermore, Valvatoidea do not belong with the Caenogastropoda, but with Heterostropha, an order not formerly
recognized and not shown here. More recently, groups within the family Pleuroceridae have been raised to family
status, so the Cerithiacea (Cerithioidea or Vermetoidea ) now contains several additional freshwater families. Click for
New classification in tabulated form.

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