Parvamussium largoi Dijkstra, 2013
DIJKSTRA, H. H. 2013. Pectinoidea (Bivalvia: Propeamussiidae and Pectinidae) from the Panglao region, Philippine Islands. Vita Malacologica, 10: 1-108, pls. 1-32, 2 tabs. [p. 19, pl. 2 figs. 6-8; pl. 4 figs. 8a-c]
2013 Parvamussium largoi Dijkstra, 2013
H. H. Dijkstra, 2013, plates 2, 4.
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«Holotype. — PMBP 2004, Stn T9, Panglao Island, off San Isidro, 9˚33.5'/33.9'N, 123˚49.5'/50.5'E, 97-120 m, alive, fine sand with seagrass, 14.vi.2004. 1 pv (NMCR-39007). Paratypes as listed below.
Other material examined. — Philippines: PMBP 2004, Stn G1, 100 m, 2 lv, 1 rv; Stn T2, 152 m, 1 lv, 1 rv; Stn T9, 97-120 m, (A), 1 pv, 6 lv, 8 rv (15 paratypes, MNHN MOLL 23192), 1 lv, 1 rv (2 paratypes, ZMA Moll. 411001); Stn T10, 117-124 m, 7 lv, 4 rv; Stn T26, 123-135 m, 3 lv; Stn T27, 106-137 m, 2 lv; Stn T39, 100-138 m, 3 lv, 1 rv.
Description. — Shell fragile, up to c. 6 mm high, transparent, left and right valves equally convex, weakly inflated, almost circular, inequivalve, equilateral, auricles almost equal in size, umbonal angle c. 90˚. Left valve with orange and milky white maculations, right valve with milky oblong white dot umbonally. Both valves smooth and glossy, with traces of commarginal growth lines on left valve, some specimens with very weak, closely spaced commarginal lamellae near the periphery of the disc. Anterior auricle of left valve smooth, some specimens with prominent commarginal lamellae near periphery, posterior auricle smooth with very closely spaced commarginal growth lines near periphery. Auricles of right valve smooth, with scales on the hinge line. Hinge line straight. Byssal notch relatively deep. Interior surface with a rudimentary short riblet on each side, one weak auricular riblet anteriorly and posteriorly.
Measurements of holotype: H 5.9 mm, W 6.5 mm, D 1.2 mm. Distribution. — Known so far from the Philippines, dead in 100-152 m, alive in 97-120 m. Etymology. — At the request of Philippe Bouchet, the specific epithet honors Dr Danilo Largo, University of San Carlos, Cebu City, Philippines, joint project co-ordinator of the Panglao Marine Biodiversity Project. Remarks. — Parvamussium largoi spec. nov. is somewhat similar to P. torresi (E.A. Smith, 1885) from the southwestern Pacific, but differs in size (P. largoi is c. 6 mm high, P. torresi is larger, up to c. 9 mm high), in external sculpture (right valve of P. largoi is smooth, right valve of P. torresi has weak commarginal lamellae) and internal sculpture (P. largoi has a few rudimentary riblets, P. torresi has 10 prominent, well developed radial ribs). Parvamussium vesiculatum Dijkstra, 1995, also known from the southwestern Pacific also has rudimentary internal riblets, somewhat similar to the present species, but differs strongly externally (P. largoi is almost smooth, P. vesiculatum is prominently sculptured)» HENK H. DIJKSTRA, 2013
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