Freshwater Molluscan Shells / Unknowns / Non-mollusks

Snail from Lake Mainit, on the
northern part of Mindanao, the
large southern island of the

It has the general aspect of one of
the viviparidae. No operculum is


From Eduardo in Spain:

These look like a Paludomus species. Paludomus loricatus Reeve 1847 to a good degree of certainty.

From a tourist shell shop near Myrtle Beach:

  Try as I might, poking through disarticulated valves,
I could not locate a matching left and right pair. So I
bought two examples of both. No clue as to species
or locality. Valves are pinkish on the interior, probably
faded due to exposure. Much of outer surface is
evenly covered by small pustules, grading to narrow
ribs on the posterior slope and near the ligament.
Some have dark rays on the posterior part of the shell.

Shells, above, approximately natural size. Hinge teeth,
left, x2.


Missouri Bootheel

Probable Cyprogenia species from a muskrat middens, St. Francis River, near Kennett, MO.
Nov. 1995. Shell has strong posterior ridge, thick anterior nacre. Surface is covered with small dark
speckles arranged in diverging bands; rough and pustulose like Cyprogenia irrorata, otherwise
more similar to C. aberti. Slightly enlarged. The consensus was it is C. aberti.

Peruvian Amazon

Small unionacean mussel from the Amazon Basin rivers in Peru, x4.

Freshwater Molluscan Shells / Non-mollusks

In an interesting example of convergent evolution, a few other freshwater organisms create mollusk-like shells.
Here are two.

Phylum Arthropoda
  Subphylum Uniramia (insects, millipedes,
  centipedes, etc)

    Class: Insecta
      Order trichoptera (caddisflies)
        Family Helicopsychidae, with a single
          Genus Helicopsyche

There are at present 203 described species. See
These small cases are constructed of sand
grains by their larvae in clear streams. Adults
resemble small delicate moths. X 8.
    Phylum Arthropoda
  Subphylum Crustacea (shrimp, etc)
    Class Branchiopoda (fairy shrimp, Daphnia
      Order Conchostraca, "clam shrimp"

There are about 200 species of clam shrimp,
comprising five families living in ephemeral and
permanent freshwater habitats worldwide.
They can swim, or may remain embedded in
the bottom. (Brusca and Brusca, 1990).
When captured, they commonly show the
front and rear appendages projecting beyond
the flexible shell. X 8 magnification. See

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