Click on photo to enlarge. Scale line in photo equals 1cm unless otherwise specified.
* Species which are commonly encountered on the beach.
photographed on an
extremely low tideCryptobranchia concentrica (Middendorff, 1847)Ringed Blind Limpetintertidal to 60m central California to northern Alaska size to 23mm
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)
Acmaeidae intertidal, Whiskey Creek Beach, WA
Acmaea mitra Rathke, 1833
Whitecap Limpet *intertidal to 60m size to 50mm
northern Mexico to northern Alaska
is commonly found intertidally. Its tall conical profile is
unmistakeable. It is frequently encrusted with coralline algae.
Family Lepetidae, Acmaeidae,
Lottiidae & Siphonariidae
photographed intertidallyLottia 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
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)
photographed intertidallyLottia 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)
photographed on kelp
washed onshoreLottia 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)
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)
intertidallyLottia 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 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.
photographed intertidallyDiscurria insessa (Hinds, 1842)Seaweed Limpet
intertidal northern Mexico to southern Alaska size to 22mm
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 comparison of similar looking species Siphonariidae Siphonaria thersites (Carpenter, 1864)Carpenter's False LimpetThis is actually an air-breathing land species. It lives on rocks closeto 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.
photographed intertidallyLottia scabra (Gould, 1846)Rough Limpetintertidal north Mexico to Cape Arago, OR size to 35mmThis
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