PROPEAMUSSIIDAE  

Parvamussium decoratum

Hayami & Kase, 1993

Figure(s)

       

rv                                             lv

holotype

Original name   Parvamussium decoratum Hayami & Kase, 1993
Autoreference   Hayami & Kase, 1993: 58, figs 182-192.
Reference   Hayami, I. & Kase, T., 1993. Submarine cave Bivalvia from the Ryukyu Islands: systematics and evolutionary significance. - The University Museum, The University of Tokyo, Bulletin 35: i-vi, 1-133, 379 figs, 6 tables, 3 maps.
Type data

  Holotype (pr: H 3.9 mm, L 4.4 mm) The University Museum, University of Tokyo, Tokyo (UMUT RM19572a). Type locality: Japan, Ryukyu Islands, Okinawa, off the southern coast of the Ie Islet, ca. 70 m, alive, byssally attached to algal balls.

Description

  Shell up to ca. 5 mm high, fragile, opaque, weakly inflated, subcircular, somewhat wider than high, inequivalve, nearly equilateral, anterior auricles slightly larger than posterior, unequal in shape, a few rudimentary internal ribs, umbonal angle ca. 100 degrees, colour dirty white.

  Left valve with reticulated sculpture of ca. 10 primary ribs and intercalated secondary radial riblets and somwhat weaker commarginal lamellae. Intersections with squamae.

  Right valve nearly smooth with delicate closely spaced commarginal lamellae. Auricles of the two valves also reticulated. Byssal notch deep, byssal fasciole narrow, ctenolium lacking.

Distribution

 

Japan, Ryukyu Islands (TL)

Habitat  Living lower littorally amongst algae and sediments.