Retusa obtusa (Montagu, 1803)

(Fig. 13D 1-D 3)

Bulla obtusa Montagu, 1803: 223 .

Utriculus obtusus – Harmer 1923: 797, pl. 63, fig. 4.

Retusa alba – Van Regteren Altena et al. 1965: 26, pl. 21, fig. 205. — Ceulemans et al. 2018: 122, pl. 7, fig. 9.

For more, see synonymy list in Ceulemans et al. (2018).

MATERIAL AND DIMENSIONS. — Maximum height 1.7 mm, width 0.8 mm. — RGM.1365120 (20), leg. AWJ; RGM.1365121 (1), leg. AWJ; RGM.1365017 (3), leg. ACJ .

SPECIES CHARACTERISATION. — Shell small, subcylindrical with low spire. Two to three teleoconch whorls separated by deeply impressed suture. Surface smooth. Aperture elongate expanded abapically.

DISTRIBUTION. — Lower Pliocene: NSB, England (Harmer 1923); Atlantic, NW France (Ceulemans et al. 2018). — Upper Pliocene: NSB, Red Crag, England (Wood 1848). — Upper Pliocene-Pleistocene: NSB, Holland (Van Regetren Altena et al. 1955). — Lower Pleistocene: Atlantic, Selsoif, NW France (this paper). — Middle Pleistocene: Atlantic, Irish Sea (Harmer 1923). Today, this species occurs in the Atlantic from Greenland, Iceland to Scandinavia, Nova Scotia to Aleutian Islands, British Isles (Thompson 1988).

REMARKS

Retusa obtusa is variable in shape and size with a more or less elevated apex (Ceulemans et al. 2018). As noted by those authors, this species is rarely reported in the fossil literature. It is predominantly a cooler water species with the most southern record being that of the Lower Pliocene of Le Pigeon Blanc (NW France).