Home > Northwest Shells & Marine Life > PNW Shells & Marine Life Photos > Bivalves >  Bivalves - Pandoridae, Lyonsiidae,
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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.



Pandoridae
Pandora filosa Pandora filosa
       San Juan Islands, WA                     south end Queen Charlotte Sound, BC
Pandora filosa Carpenter, 1864
Western Pandora
subtidal, 20-300m          northern Mexico to central Alaska          size to 27mm
This shell has an elongated tip.  As with all Pandora, one valve is flat, while the other is inflated.  Small specimens may have sand particles on the periostracum.
(synonyms - Pandora gouldii, Lyonsia haroldi, Lyonsia nesiotes)
















Pandora wardiana Pandora wardiana
   San Juan Islands, WA                        San Juan Islands, WA
Pandora wardiana A.Adams, 1860
Giant Pandora
subtidal, 5-400m          size to 76mm
Oregon to northern Alaska; Japan to Siberia
This is the largest species of Pandora.  The posterior end is prominently rounded, separated by a distinct furrow from the anterior end.
(synonyms - Pandora grandis, Pandora forresterensis)        


Lyonsiidae
Entodesma navicula Entodesma navicula Entodesma navicula
                   Petersburg, AK                                                     Anacortes, WA, intertidal                                 Port Angeles,WA, subtidal
Entodesma navicula (A.Adams & Reeve, 1850)
Northwest Ugly Clam *
intertidal to 60m          northern Mexico to northern Alaska; Japan          size to 150mm
This is commonly found intertidally.  It lives nestled in rocks and therefore its shape can be somewhat variable.  The shell grows distorted and has a thick, periostracum which has folds in it.  The interior is nacreous.  The shell is usually covered with grit and encrustations and can easily go unnoticed between the rocks.
(synonym - Entodesma saxicola)






Pandora punctata
Esperanza Inlet, Vancouver Island, BC
Pandora punctata Conrad, 1837
Punctate Pandora
subtidal to 50m          size to 45mm
northern Mexico to Esperanza Inlet,
Vancouver Island, BC
This shell has a strongly curved shape.








Verticordiidae
Mytilimeria nuttallii Mytilimeria nuttallii Mytilimeria nuttallii
               Haida Gwaii, BC                        Hope Island, BC                     Whidbey Island, WA, subtidal
Mytilimeria nuttallii Conrad, 1837
Bladderclam
intertidal to 70m          size to 47mm
northern Mexico to southern Alaska
This is rarely found intertidally.  The shell is very fragile.  It is usually covered with tunicates so hard to see and dead shells break apart very quickly.  It can be somewhat variable in shape.
Thracia trapezoides Thracia trapezoides
                                              Victoria, BC                                                                           Barkley Sound, BC                 
Thracia trapezoides Conrad, 1849
Trapezoidal Thraciid
subtidal, 11-200m          northern Mexico to southern Alaska          size to 65mm
This shell is rarely seen. It is generally more angular in appearance than the other Thracia species.  As with the others, it lives in sand and mud.  The right valve is slightly larger than the left.
















Cardiomya planetica
Barkley Sound, BC
Cardiomya planetica (Dall, 1908)
Fine-Ribbed Cardiomya
subtidal, 25-3000m          Panama to northern Alaska; Galapagos; Japan          size to 30mm
This species has numerous, small ribs with a long, narrow rostrum.  It lives in mud.
(previous name - Cuspidaria planetica)













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Cuspidariidae
Cardiomya pectinata
Burrard Inlet, BC
Cardiomya pectinata (Carpenter, 1864)
Ribbed Dipper
subtidal, 5-1000m          Ecuador to central Alaska; Galapagos          size to 40mm
This species has prominent radial ribs.  The elongated rostrum may be either straight or slightly curved.   It lives in sand and mud and grows larger in its northern range than in does in the south.
(synonyms - Cardiomya oldroydi, Cuspidaria californica)





Lyonsia californica Lyonsia californica
          Southern Gulf Island, BC, subtidal                                       San Juan Islands, WA, subtidal












Lyonsia californica Conrad, 1837
California Lyonsia
intertidal to 100m          size to 42mm
south Mexico to central Alaska
This fragile shell is very rare to find intertidally. There are fine radial lines on the periostracum.  Sand tends to adhere to the periostracum, especially in younger specimens.
(synonyms - Lyonsia gouldii, Lyonsia haroldi, Lyonsia nesiotes)

Lyonsia californica
slightly variable and often with sand adhered to it




























Thraciidae
Thracia challisiana
Seymour Inlet, BC
Thracia challisiana Dall, 1915
Pustulose Thraciiid
subtidal, 30-230m          size to 60mm
north Mexico to south Alaska
This rare shell has a coarsely granular surface and the right valve is slightly larger than the left. 





















Thracia myopsis
central Queen Charlotte Sound, BC
Thracia myopsis Möller, 1842
Arctic Thraciid
subtidal, 50-250m          size to 40mm
Panarctic and circumboreal, reaching south to central California, the Sea of Japan, Massachusetts and Norway
In this rare shell the right valve is more inflated than the left.  It also has a granular surface.























































































Bivalves 

Family Pandoridae, Lyonsiidae,

Verticordiidae, Thraciidae & Cuspidariidae


This page last revised: 5-25-2019