Freshwater Mollusks - U.S. Fish and Wildlife Service

Ferrissia rivularis tributaries, rivers, reservoirs
T his species belongs to a group of snails called “limpets.”
They’re interesting snails, and as you can see, they are unusual
in shape. The Ferrissia rivularis, or creeping ancylid, is common
across North America in streams, lakes, and marshes.
In southern Idaho, it is the most common limpet and
is found in most streams.
Ferrissia rivularis is found in gravel to cobble substrates in
large rivers or tributaries, but may also be found in substrates
ranging from mud to boulder to aquatic vegetation.
This limpet will tolerate areas that are nutrient-rich
(reservoirs, ponds, marshes). It’s relatively
small; about 6 mm long and