Lacuna crassior (Montagu, 1803)

(Fig. 7C 1-C 3)

Turbo crassior Montagu, 1803: 309, pl. 20, fig. 1.

Lacuna crassior – Harmer 1921: 667, pl. 53, figs 27-29. — Fretter & Graham 1980: 247, fig. 198. — Moerdijk & Janse 2015: 22, fig. 9.

MATERIAL AND DIMENSIONS. — Maximum height 10.2 mm (incomplete), width 6.3 mm. — RGM.1365195 (1), leg. WG; RGM.1364912 (2), leg. WG; RGM.1365173 (1), leg. ACJ; RGM.1365096 (17), leg. AWJ .

SPECIES CHARACTERISATION. — Smooth, medium-sized shell. Protoconch damaged or lacking in almost all specimens, but in a few specimens the first whorl is flat and not clearly separated from the teleoconch. Teleoconch of four round whorls. Aperture typically circa 40% of shell height. Umbilicus reduced to narrow slit.

DISTRIBUTION. — Lower Pleistocene: NSB, England (Harmer 1921); Atlantic, Selsoif, NW France (this paper). — Holocene: England (Harmer 1921), West Greenland (Símonarson 1981). Beached occurrences of this species likely of a Late Pleistocene age are known from The Netherlands (Moerdijk & Janse 2015). Today this species occurs from Greenland, Arctic Canada to the British Isles and Normandy (Fretter & Graham 1980; Backeljau et al. 1984). The species has been reported living on or near the fleshy bryozoan Alcyonidium from between the low water tide line to 90 m water depth in areas with stones, rocks and shells dispersed in soft substratum (Graham 1988).