Gastropods

Click on photo to enlarge. Scale line in photo equals 1cm unless otherwise specified.
* Species which are commonly encountered on the beach.

Calyptraeidae

Whiskey Creek Beach, WA Anacortes, WA, intertidal

Calyptraea fastigiata Gould, 1846
Cup-and-Saucer Snail
intertidal to 137m southern California to central Alaska size to 25mm
This is occasionally found intertidally. It can easily be confused with the Whitecap Limpet until it is overturned. This shell has a partial shelf on the underside. It is also a thinner shell than the limpet.

Hipponicidae

Makah Bay, WA
Antisabia or Hipponix sp.
Flat Hoofsnail
intertidal to subtidal size to 25mm
This is infrequently found on the open coasts. The shell shape and growth are irregular and often encrusted. It clings to rocks.
The Pacific Northwest hoof snails are still under study. More than one species is present.

Crepidula convexa Say, 1822
Atlantic Convex Slipper-shell
intertidal size to 20mm
southern California to southern BC; Caribbean to Massachusetts
This is infrequently found. It was introduced to the west coast from the Atlantic. It looks similar to our native C. adunca except that the the apex is folded far forward. In the northwest it is only found in isolated populations. It is usually attached to dead shells in our area.
(synonym - Crepidula glauca)

Waddah Island, WA

Crepidula nummaria Gould, 1846
Northern White Slipper-shell
intertidal to subtidal size to 46mm
northern California to BC
This species is found on the outer coast attached to rocks or dead shells. It typically has a shaggy brown periostracum. There is a notch on the left edge of the interior shelf. The interior is glossy white.

Penrose Point, WA Big Fishtrap Cove, WA, intertidal

Crepidula fornicata (Linnaeus, 1758)
Eastern Slipper-shell
intertidal Texas to Canada; introduced to Washington and BC, Japan and Europe size to 50mm
This is usually common to find where it has established a population within the Salish Sea. The shell usually has brown spots or blotches. It has a thin brown periostracum which is often worn away. The interior has a bright white shelf. Then shell is generally inflated. On the east coast it is often found in stacks of several shells on top of each other. In our area we rarely observe more than one male on top of a female shell.

Crepidula fimbriata Reeve, 1859
Frilled Slipper-shell
intertidal to subtidal size to about 30mm
San Juan Islands, WA to south AK

This species prefers protected and transitional waters rather than the outer coast. It is found on rocks and dead shells. It often has frilled margins and a dark brown interior stain but these features may also be absent. It has no periostracum. This species often identified as C. perforans before that species was known to only be on the outer coast.

Baja California, Mexico
Crepidula norrisarium Williamson, 1905
intertidal to subtidal size to 35mm
northern Mexico to BC
This species prefers the protected waters within the Salish Sea. It has been long confused with C. adunca and has a similar appearance. This shell has a more blunt apex and does not have the pit in the shelf. It frequently carries its juveniles on its back whereas the juveniles of C. adunca quickly crawl away.

Crepidula perforans (Valenciennes, 1846)
Western White Slipper-shell
intertidal to subtidal size to 40mm
northern Mexico to Kodiak, AK

This species is found on the outer coast where it resides under rocks. It can sometimes be found in the holes of boring clams. The shell is smooth and white with a glossy interior. It tends to have an elongated shape and a thin, light-colored periostracum.

Crepidula williamsi Coe, 1947
Hermit Crab Slipper-snail
intertidal to at least 30m size to 40mm
California to Alaska

This species is commonly found inside the aperture of dead snail shells which are also occupied by hermit crabs. It may also be found on other dead shells. The shell is mainly white with a dark stain or radiating lines on the tip of the apex. It is also elongated in shape.

Species in the Calyptraeidae family are sequential hermaphrodites, meaning they change sex at some point during their life. In the case of the Slipper shells, one often sees a large female shell with one or more smaller males attached to the back of its shell. As the female ages and dies, the males grow and morph into females, with new young males attaching to their shells.

Bremerton, WA Big Fishtrap Cove, WA, intertidal

Crepipatella lingulata (Gould, 1846)
Wrinkled Slipper-shell *
intertidal to 100m Mexico to northern Alaska size to 25mm
This is commonly found intertidally. The shell is mostly circular but irregular based on the surface where it is living. The exterior is somewhat wrinkled with a thin periostracum. Tan to mauve blotches may also be evident. The apex is near the margin. On the interior the small shelf sits under the apex. This has frequently been called C. dorsata, but that is now considered a tropical species.
(synonyms - Crepidula lingulata, Crepidula fissurata)

Whiskey Creek Beach, WA Neah Bay, WA, intertidal Whiskey Creek Beach, WA, intertidal

Crepidula adunca G.B. Sowerby I, 1825
Hooked Slipper-shell
intertidal to 19m northern Mexico to south Alaska size to 25mm
This species is found on the outer coast and in transitional waters. It is frequently attached to other shells such as Calliostoma, Tegula, Nucella and Lirabuccinum. It may also be found on rocks. The shell is brown with a brown periostracum. The interior is chocolate brown with a white shelf. The apex is usually high and hooks forward. The hooked apex creates a pit within the shelf in the interior.
(synonym - Garnotia adunca)

Bremerton, WA Bremerton, intertidal

Crepidula onyx (Sowerby, 1824)
Onyx Slipper-shell
intertidal to 90m Chile to southern California; Washington size to 70mm
This was introduced to Puget Sound. It is occasional found where it has established populations. This shell has a yellowish-brown periostracum and occasional brown markings. The interior is chocolate brown with a bright white shelf.

Family Hipponicidae & Calyptraeidae