Home > Northwest Shells & Marine Life > PNW Shells & Marine Life Photos > Gastropods >  Gastropods - Lepetidae, Acmaeidae,
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Click on photo to enlarge.  Scale line in photo equals 1cm unless otherwise specified.
* Species which are commonly encountered on the beach.

Cryptobranchia concentrica Cryptobranchia concentrica
                                                       photographed on an extremely low tide
Cryptobranchia concentrica (Middendorff, 1847)
Ringed Blind Limpet
intertidal to 60m          central California to northern Alaska          size to 23mm
This is infrequently found intertidally.  It has a smooth white shell with a low profile.  There is another small white limpet, Lepeta caeca, also rarely seen, which has small pustules on its shell which can distinquish it from this species.
(previous name - Lepeta concentrica)

Acmaea mitra
intertidal, Whiskey Creek Beach, WA
Acmaea mitra
Rathke, 1833
Whitecap Limpet *
intertidal to 60m          size to 50mm
northern Mexico to northern Alaska
This is commonly found intertidally.  Its tall conical profile is unmistakeable.  It is frequently encrusted with coralline algae.


Family Lepetidae, Acmaeidae,

Lottiidae & Siphonariidae

Lottia asmi

Lottia fenestrata Lottia fenestrata
                                                                                                              photographed intertidally
Lottia fenestrata (Reeve, 1855)
Fenestrate Limpet or Chocolate Limpet
intertidal          northern Mexico to Alaska          size to 26mm
This species is infrequently found.  It lives in the lower intertidal zone and is usually found at the base of rocks
burrowed into the sand at low tide.    The top of the shell is usually eroded and it can be difficult to identify without
seeing the interior of the shell.  The interior may be a solid dark chocolate brown to a lighter brown with only a dark
 lower ring.  The apex is slightly off center.
(previous names - Tectura fenestrata, Notoacmaea fenestrata, Collisella fenestrata, Acmaea fenestrata, Acmaea cribraria)

Lottia digitalis Lottia digitalis
                                                                                                           photographed intertidally
Lottia digitalis (Rathke, 1833)
Ribbed Limpet or Finger Limpet *
intertidal          northern Mexico to northern Alaska          size to 35mm
This is commonly found in the higher intertidal zone.  It lives among the barnacles.  The apex is far forward
on the shell and it has distinct ridges.  It is generally patterned with brown markings and spots.  This species
is hard to confuse with any other.
(previous names - Collisella digitalis, Acmaea digitalis, Collisella austrodigitalis, Acmaea radiata)

Lottia instabilis Lottia instabilis
                              kelp form                                        photographed on kelp washed onshore
Lottia instabilis (Gould, 1846)
Unstable Limpet *
intertidal to 73m          southern California to northern Alaska          size to 35mm
This species is generally easy to find, although it is usually as a dead shell washed ashore.
The most recognizeable form of this species has a distinct oval shape and high profile.  It lives on
the stipes of kelp.  This species also has an ecomorph which lives on rocks in the intertidal zone.
The rock morph is very difficult to separate from the other common intertidal species as it exhibits
the same striped markings and profile, although it has parallel sides.  The rock morph used to
be described under the name Lottia ochracea.
(previous names - Notoacmaea instabilis, Collisella instabilis, Acmaea instabilis)

Lottia asmi (Middendorff, 1847)
Black Limpet
intertidal          northern Mexico to southern Alaska          size to 10mm
This species is hard to find.  It generally lives on the shell of the Black Turban, Chlorostoma funebralis.  The color of the limpet blends with the color of turban shell.
(previous names - Collisella asmi, Acmaea asmi)


Lottia parallela Lottia parallela Lottia parallela
                                                                                                            photographed in tidepools
Lottia parallela (Dall, 1921)
Pacific Eelgrass Limpet *
** Preliminary studies are indicating that this is simply an eelgrass morph of Lottia pelta **

Lottia pelta Lottia pelta Lottia pelta
                                                                                                    photographed intertidally            feeding trail on a rock
Lottia pelta (Rathke, 1833)
Shield Limpet *
intertidal          northern Mexico to northern Alaska;  Siberia          size to 54mm
This is very commonly found and is one of our most abundant limpets.  It has a highly variable shape and coloration depending on its
habitat.  It generally has a high apex which is slightly forward on the shell.  The front of the shell is normally narrower than the rear.  
When not highly eroded by waves or encrustations, it exhibits radial ribbing.  The color may be light to dark with radial banding.  
The shell is frequently covered by algae or encrustions.  This species may have several ecomorphs.
(previous names - Collisella pelta, Acmaea pelta, Acmaea cassis, Acmaea olympica, Acmaea nacelloides)

Lottia persona Lottia persona
                                                                                                                     photographed intertidally
Lottia persona (Rathke, 1833)
Mask Limpet *
intertidal          northern Mexico to northern Alaska          size to 50mm
This is a very commonly found species.  It lives in the very high intertidal zone.  The interior may be white to
 bluish with a dark band at the base.  The exterior may have varying amounts of patterning.  Juveniles often
show faint radial ribs, but these become obscured on older specimens.  The shell also becomes significantly
higher as it ages.  These shells are rarely obscured by algae or other overgrowth.
(previous names - Tectura persona, Notoacmaea persona, Acmaea persona, Collisella radiata)

Lottia rosacea Lottia rosacea Lottia rosacea
                                                                                                                                     photographed intertidally
Lottia cf. rosacea (Carpenter, 1864)
Pacific Rosy Limpet
low intertidal to subtidal          California to BC?          size to 8mm
This species is rarely seen.  Preliminary studies show this species may not be the same as Lottia rosacea, which is
described from specimens in California.   Even within California, this name may represent a group of similar species.
Locally our specimens have light brown to pinkish markings, an oval shape and slightly off center apex.  

Lottia triangularis
Lottia triangularis (Carpenter, 1864)
Triangular Limpet
low intertidal to subtidal          size to 8mm
California to BC?
This species is rarely seen.  There are two forms.
The elongated form is shown above and it is often
white and encrusted with coralline algae.  A more
compressed, wider form lives on the stipes of
 corallines and exhibits more markings.

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Discurria insessa Discurria insessa
                                                                                               photographed intertidally
Discurria insessa (Hinds, 1842)
Seaweed Limpet
intertidal          northern Mexico to southern Alaska          size to 22mm
This species is hard to find.  It feeds on the feather boa kelp but is very difficult to spot.  It has a relatively smooth brown surface and is difficult to confuse with any other species.
(previous names - Notoacmaea insessa, Collisella insessa, Acmaea insessa, Patella insessa)

Lottia scutum Lottia scutum Lottia scutum
                                                                   photographed intertidally              note the brown tentacles
Lottia scutum (Rathke, 1833)
Pacific Plate Limpet *
intertidal to shallow subtidal          northern Mexico to northern Alaska; Japan; Siberia          size to 64mm
This is a very common species.  It is very similar in appearance to L. pelta.  This shell has a smooth surface and a rather brittle outer edge.  The tentacles of the animal are brown which also distinguish it from our other limpets whose tentacles match the animals' body color.  The apex may be low or high and otherwise has typical markings for the limpets of our area.  The shell surface is often covered in algaes or seaweeds.
(previous names - Tectura scutum, Notoacmaea scutum, Acmaea scutum, Acmaea testudinalis scutum)

Lottia comparison
Lottia comparison of similar looking species

Siphonaria thersites
Siphonaria thersites (Carpenter, 1864)
Carpenter's False Limpet
This is actually an air-breathing land species. It lives on rocks close
to the high tide level and can sometimes be found dead on the beach.
We include it here because it is easily mistaken for a marine limpet, although it is uncommon to find.

Lottia scabra Lottia scabra
photographed intertidally
Lottia scabra (Gould, 1846)
Rough Limpet
intertidal          north Mexico to Cape Arago, OR          size to 35mm
This limpet is found only at the very southern portion of the "Pacific Northwest".  It lives in the upper mid-intertidal to the high intertidal and prefers a horizontal surface.  Its prominent ribs form a scalloped margin to the shell.  This species returns to a "home spot" on the rock at low tide.  In the right photo, the home depression is visible in the easily worn sandstone.  Our photos were taken at Cape Arago.
(previous names - Collisella scabra, Macclintockia scabra, Acmaea scabra)

This page last revised: 8-23-2014