Glycymeris bimaculata (Poli, 1795)
Mediterranean. Sublittoral to at least upper shelf, on sandy bottoms. Original taxon: Arca bimaculata. One of the largest members of the genus.
Synomym: Petunculus siculus Reeve. (siculus = sicilian).
Trawled at 70-80m deep, Málaga, Andalucia, S. Spain. 90mm.
Pectunculus bimaculatus in Pereira da Costa & al.: Mollusques tertiaires du Portugal — planches, Lisboa 1903-1904.
Trawled on mud at 80-110m deep, off Roses, Girona, Catalunya, NE. Spain. 62mm.
Arca bimaculata in G. Poli: Testacea utriusque Siciliae… vol. II, Parma 1795 (description p. 143) and in vol. IV 1791-1796 (illustration pl. XXV) via BHL.
 
« Shell perfectly lentiform, covered with longitudinal obsolete striae and a compact, silky periostracum; two snowy splashes near the umbones; margin crenulate. » These snowy or milky splashes gave the species its name. Unfortunately, the illustration doesn’t show them, but they can be seen in my first picture on top of page. In fact, the only useful distinctive feature is given by the umbones, which are strictly orthogyre in bimaculata, and never in the other european members of the genus. You can see, at the glycymeris page, near the bottom, a bimaculata-like specimen that could lead to confusion, except that its umbones are not correct.
Pectunculus bimaculatus in J. G. Hidalgo: Moluscos marinos de España, Portugal y las Baleares, Madrid 1870, via BHL.

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