ID Guide: California Coast Marine Invertebrates

Color varies from bright red to dark reddish-purple. Distinguished from purple urchins (Strongylocentrotus purpuratus) by its larger test and proportionally longer spines.

Bright purple coloration. Most common urchin to find exploring rocky intertidal zones.

[pictured: test]

Can have five to six arms, found in a variety of colors ranging from purple to orange to red.

Coloration varies from vibrant purple to dull red to vibrant orange.

Part or all of column tends to be buried. Tentacles have white bands, but color varies widely.

Distinguished from aggregating anemone by larger size and green tentacles with minimal color variation or striations. Distinct radial striation present on oral disc.

Distinguished from sunburst anemone (Anthopleura sola) by little to no radial striation on the oral disk.

[pictured: retracted]

Distinguished from other Epiactis spp. by the presence of small anemone around the bottom of the column of a larger parent anemone.

[pictured: side view of larger anemone with smaller anemone along its column]

Differentiated from other anemone genus by small white/pale lines radiating from the edge of the anemone. Particularly noticeable on retracted anemone. Vary widely in coloration.

[pictured: retracted]

[pictured: retracted]

Distinguished by dark/muted brown coloration with small, pale dots on legs.

[pictured: a molting kelp crab beneath its molt]

Color varies, typically camouflaged to the color of kelp the isopod is on or under. [pictured: kelp isopod on feather boa kelp (Egregia menzisii)]

Distinguished from buckshot barnacles (Chthamalus spp.) by relatively larger size and ridged plates. White to tan coloration with a distinct diamond shaped operculum.

One of the largest species of barnacle in the world. Can grow up to over 3" diameter.

Tiny tan to brown barnacles with smooth plates and round operculums.

Large barnacles with distinct shape often found growing with California mussels (Mytilus californianus).

Similar shape to the pink volcano barnacle (Tetraclita rubescens), but white or grey in coloration.

Larger species of barnacle with distinct pink to red coloration and ridges.

[pictured: siphon tip]

[pictured: shell]

[pictured: shell]

Often found growing with gooseneck barnacles (Pollicipes polymerus).

Exact species often difficult to distinguish due to interbreeding between the native M. trossellus, and non-native M. edulis.

Distinguished from wart-necked piddock (Chaceia ovoidea) by lighter coloration with denser light dots on siphon tips. [pictured: siphon tip]

Distinguished from a sea lemon (Peltodoris nobilis) by smaller size and yellow gills. Dark speckles appear only on its tubercles.

Distinguished from a sea lemon (Peltodoris nobilis) by more muted coloration and often a distinct patch of dark speckles above white gills.

Bright yellow dorid covered with dark speckles between tubercles. White gills. Largest yellow dorid on the Central California Coast.

[pictured: angular unicorn with eggs]

Often found on kelps. [pictured: seaweed limpet on feather boa kelp (Egregia menzisii)]

The largest Lottia species. Shell can grow up to over 4" in diameter.

Distinguished from other Lottia spp. by the distinct deep radial ridges on its shell.

Distinct light and dark radial stripes. Pattern of stripes highly variable.

A genus that encompasses many species of limpets found in California.

Shell can be found in various stages of weathering, from sharp 'frills' to smooth. Coloration varies from bright orange to dark brown.

One of the most common chitons to find in Half Moon Bay high tide.