Fig. 4 g–i
Mytilus (Dacrydium) hyalinus Monterosato, 1875 [a] (p. 10).
Dacrydium hyalinum (Monterosato, 1875) — Nordsieck 1969 (p. 30); Mattson & Warén 1977 (p. 1, figs. 3, 9); Salas & Gofas 1997 (p. 266, figs. 20–24); Önen & Doğan 2007 (p. 236, fig. 3).
Dacrydium cf. hyalinum Monterosato, 1875 — Salas 1996 (p. 53, figs. 91–93).
Dacrydium hyalinum Monterosato, 1875 — Giannuzzi-Savelli et al. 2001 (p. 132, figs. 236–238); Repetto et al. 2005 (p. 294, mid right fig.); Peñas et al. 2006 (p. 140, figs. 389–395).
Diagnostic characters. Much higher than long, bean-shaped shell; small beaks; very short anterior side; convex antero-ventral margin nearly parallel to the postero-dorsal one. Prodissoconch: shell type ST-2D; length about 170 µm; roundish D-shaped outline; convex profile; P-1 surface pitted, with roughly commarginal, irregular wrinkles; rim-like metamorphic lip barely separated from P-1; transition to the nepioconch well marked.
Occurrence. Box-corer sample BC72 (4 specimens); core BC72 (2). Maximum height: 2 mm.
Distribution and habitat. Dacrydium hyalinum appears to be endemic of the Mediterranean Sea, from the western basin to Turkey, although similar forms have been reported from some North Atlantic seamounts; it occurs on circalittoral to bathyal hard bottoms (frequently corals), as well as on mud and sand (Nordsieck 1969; Salas & Gofas 1997; Önen & Doğan 2007).
Fossil record. Bathyal Pleistocene of Sardinia (Di Geronimo & Bellagamba 1985).