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Rictaxis punctocaelatus Rictaxis punctocaelatus
        Doheney Beach, CA                 Hornby Island, BC, subtidal

Order Cephalaspidea
Many species in this order have a shell, and are commonly referred to as Bubble Shells.  A few only have vestigial shells which are hidden inside the mantle.    

Rictaxis punctocaelatus (Carpenter, 1864)
Striped Barrel Shell
intertidal to 100m          northern Mexico to southermost Alaska          size to 20mm
This is infrequently found intertidally in the northwest.  It lives on sand and glides just
underneath the surface of the sediment, usually just below eelgrass beds.
(previous name - Tornatella punctocaelata)

Retusa obtusa
Saltspring Island, BC
Retusa obtusa (Montagu, 1803)
Arctic Barrel-Bubble
intertidal to 300m          shell size to 10mm
southern BC to Alaska; north Atlantic
Burrows in mud or muddy sand just within a few centimeters of the surface

Haminoea vesicula Haminoea vesicula Haminoea vesicula
               Birch Bay, WA                         Oak Bay, WA, intertidal, with eggs           Birch Bay State Park, WA, intertidal
Haminoea vesicula Gould, 1855
White Bubble Shell

intertidal to shallow subtidal          northern Mexico to southern Alaska          size to 24mm
This is the most commonly found bubble shell in the Pacific Northwest.  It lives on eelegrass and mud in sheltered bays.  It can be very abundant during spring and summer while laying its eggs.  The bright yellow egg ribbons are easy to spot.  The shells are thin and fragile and break easily once the animal dies.  For this reason, dead shells are not commonly found.

Acteocina eximia
 off Grebe Islets, BC
Acteocina eximia
(Baird, 1863)

Pleatless Barrel-Bubble
intertidal to subtidal on sand and mud
shell size to 13mm
central California to central Alaska
(synonyms - Acteocina culcitella intermedia, Bullina eximia)

Haminoea japonica Haminoea japonica Haminoea japonica
                      Boundary Bay, BC                                             Boundary Bay, BC, intertidal                               Thetis Island, BC,intertidal
Haminoea japonica (Pilsbry, 1895)
Oval Bubble Shell
intertidal on eelgrass and sand     San Francisco Bay, California; northern Washington to southern BC; Japan     size to 35mm
This is found only in the locations where it has been introduced and is often alongside H. vesicula.  The shells are very similar.   On the live animal, H. japonica has a deeply bifurcate cephalic shield.
(previously called Haminoea callidegenita when found in the eastern Pacific)

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Aglaja ocelligera
Birch Bay State Park, WA, intertidal
Aglaja ocelligera (Bergh, 1894)
Spotted Aglaja
very shallow subtidal to 20m on mud bottoms          size to 20mm
southern California to southern Alaska
It has a vestigial internal shell. This is a small species and while it is normally subtidal, it is possible to find it on a very low tide near the water's edge which is where this one was photographed.
(previous name - Doridium ocelligerum)  

This page last revised: 6-14-2019
Haminoea virescens
west coast WA
Haminoea virescens (Sowerby, 1833)
Green Bubble Shell
intertidal          Panama to Alaska          size to 18mm
This is found only on rocky, open coast habitat.
Acteocina culcitella
Tunstal Bay, BC
Acteocina culcitella
(Gould, 1853)

Western Barrel-Bubble
intertidal to 46m on sand and mud  
shell size to 22mm
northern Mexico to central Alaska

(previous name - Cylichnella culcitella, Bulla culcitella)

Gastropteron pacificum Gastropteron pacificum Gastropteron pacificum 
      Friday Harbor, WA, subtidal               Freshwater Bay, WA, subtidal                Lopez Island, WA, subtidal


Diaphana californica
Rich Passage, WA, subtidal
Diaphana californica Dall, 1919
California Diaphana
intertidal to shallow subtidal          size to 5mm
northern Mexico to northern Washington
This is rarely found intertidally, partly due to its small size.  The shell is extremely thin and is similar in shape to the other bubble shells, but with a flat apex.  The animal is white.

Gastropteron pacificum
in and near Rich Passage, WA, subtidal

Gastropteron pacificum Bergh, 1894
Pacific Stomach Wing
intertidal to 425m          size to 40mm
northern Mexico to northern Alaska; Galapagos
This is infrequently found intertidally.  This species may be readily seen when it is swimming.  When buried in the sediment, it is a small lump in the mud.  
(For more insight into this creature,
see Ron Shimek's Blog posting of August 8, 2011.)

Melanochlamys diomedea
Rich Passage, WA, subtidal
Melanochlamys diomedea (Bergh, 1893)
Diomedes' Aglaja
intertidal to113m          size to15mm
southern California to Alaska
It has a vestigial internal shell.  It is very similar in appearance to Aglaja ocelligera, but without the white spots.  It is light cream with brown and black mottling which can completely hide the cream color.
(synonyms - Aglaja diomedea, Aglaja nana, Aglaja ezoensis)

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

Superfamily Acteonoidea


Nudibranchs and other Sea Slugs

Superfamily Acteonoidea

Order Cephalaspidea