Crepidula perforans (Valenciennes, 1846)

Common name(s): Western white slipper shell, Western white slipper snail

Synonyms: Crepidula williamsi
Phylum Mollusca
 Class Gastropoda
  Subclass Prosobranchia
   Order Mesogastropoda
    Suborder Taenioglossa
     Family Calyptraeidae
Crepidula perforans attached inside the aperture of a whelk shell which is occupied by a hermit crab
(Photo by: Dave Cowles, July 2005)
Description:  A slipper shell which is a flattened or even concave, irregular cap-shape with an apex directed posteriorly, white, with the free margin of the septum nearly straight, often attached to bivalve shells, especially inside those occupied by hermit crabs.  Length up to 5.5 cm but usually not much over 2.5 cm.  Variable in shape, conforms to substrate.  May be thin and fragile or thick and robust.  Periostracum thin, often inconspicuous.

How to Distinguish from Similar Species: Crepidula nummaria has a yellow-brown periostracum.  Crepidula fornicata has the apex to the side.  Few other species besides this one live inside gastropod shells with hermit crabs.

Geographical Range:  Vancouver Island to Baja California

Depth Range:  Almost completely subtidal in Puget Sound

Habitat:  Occasionally on rock, often inside apertures of shells, inside holes of rock-boring clams.

Biology/Natural History:  In Alaska, is sometimes found on the operculum of the Oregon (hairy) triton, Fusitron oregonensisCrepidula nummaria may be synonymous with this species.  The systematics needs to be worked out better.  The females brood their young, which can distinguish this species from C. nummaria.

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Dichotomous Keys:
  Flora and Fairbanks, 1966
  Kozloff 1987, 1996
  Smith and Carlton, 1975

General References:
Harbo, 1997
Kozloff, 1993
Morris et al., 1980
O'Clair and O'Clair, 1998
Ricketts et al., 1985

Scientific Articles:

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

A shelf occupies the anterior portion of the shell.  Scale below is cm with mm marks.  Photo by Dave Cowles July 2005

Authors and Editors of Page:
Dave Cowles (2005):  Created original page