PROPEAMUSSIIDAE  

Parvamussium alaskense

(Dall, 1871)

Figure(s)

   

lv                                                     rv

Alaska, Pribilof Island area

lv                                                     rv

Original name   Pecten (Pseudamusium?) alaskensis Dall, 1971
Autoreference   Dall, 1871: 155, pl. 16, figs 4a-b.
Reference   Dall, W.H., 1871. Descriptions of sixty new forms of mollusks from the West coast of North America and the North Pacific Ocean, with notes on others already described. - American Journal of Conchology 7: 93-160, pls 13-16.
Type data   Syntypes (pr + rv) not traced in the National Museum of Natural History, Washington DC (USNM). Type locality not specified: Alaska, Unga Island, North Harbor, 11 m, mud, dead (rv); Chugach Gulf, Port Etches, alive (pr) (USRS "Wyanda").
Description

  Shell up to ca. 30 mm high, fragile, semi-transparent to opaque, weakly inflated, nearly circular, left valve slightly more convex than right valve, inequivalve and equilateral, anterior auricles much larger than posterior, unequal in shape, internal ribs variable in length and number, usual ca 20, colour left valve creamy or whitish with an orange umbonal spot, right valve whitish.

  Left valve with numerous radial scaly riblets (20-30) and intercalated secondary riblets. Anterior auricle more prominent radially sculptured than posterior.

  Right valve with closely spaced, delicate commarginal lamellae. Anterior auricle coarse radially sculptured and weak commarginally, posterior auricle commarginally sculptured. Byssal notch relatively deep, byssal fasciole and ctenolium lacking.

Distribution

 

Japan, Sea of Okhotsk, Bering Sea, Chukchi Sea, Alaska (TL) southwards to California

Habitat  Living littorally to bathyally on muddy bottoms.