Neptunea inversa Harmer, 1918

Neptunea inversa Harmer, 1918 View in CoL

( Fig. 11E View FIG 1-E View FIG 3 View FIG )

Neptunea contraria var. informis Harmer, 1918 View in CoL (partim): 367, pl. 36, figs 30-31 [not pl. 16, fig. 6, that corresponds to Neptunea contraria (Linnaeus, 1771) forma informis Harmer, 1914] (non Harmer, 1914).

Neptunea antiqua (Linnaeus) var. inversa Harmer, 1918 View in CoL (partim): 368, pl. 36, fig. 26 [not fig. 28, that corresponds to Neptunea contraria (Linnaeus, 1771) ].

Neptunea inversa View in CoL – Vervoenen et al. 2014: 31, figs 24-26. — Wesselingh et al. 2014: 196, fig. 10. — Preece et al. 2020: fig. 7e.

MATERIAL AND DIMENSIONS. — Maximum height 50.2 mm, width 31.9 mm (incomplete). — RGM.1364923 (18), leg. WG ; RGM.1365006 (26), leg. ACJ ; RGM.1365188 (1), leg. ACJ ; RGM.1310340 (1), leg. ACJ ; RGM.1365110 (1), leg. AWJ .

SPECIES CHARACTERISATION. — Relatively small, s inistral Neptunea species with flat whorl profile and shallow suture. Shell smooth or with low spiral cords separated by faint spiral grooves; thickened axial growthlines on the bigger specimens. Aperture elongate with an open siphonal canal. Juveniles are common in the studied material with a prominent protoconch.

DISTRIBUTION. — Lower Pleistocene: NSB, Norwich Crag and Weybourne Crag, England (Harmer 1918; Preece et al. 2020); Atlantic, Selsoif, NW France ( Vervoenen et al. 2014). — Lower-Middle Pleistocene: Channel region, England ( Vervoenen et al. 2014). — Middle Pleistocene: Irish Sea (Harmer 1918). — Pleistocene (indeterminate): Netherlands ( Vervoenen et al. 2014).

REMARKS

Neptunea inversa Harmer, 1918 differs from N. contraria (Linnaeus, 1771) in being smaller, lower spired, with less convex whorls separated by a shallower suture. It is a marker species for early-middle Pleistocene assemblages of the southern North Sea Basin, Channel and Irish Sea ( Vervoenen et al. 2014). Those authors noted than the specimen from Selsoif has slightly more convex whorls than usual for specimens of N. inversa from Early and Middle Pleistocene localities (not Late Pleistocene; lapsus). Adult specimens are uncommon in Selsoif where the species is represented by hundreds of juveniles. However, one of the specimens illustrated (Pl. 6, fig. 9) has a low spire and very flat whorls in keeping with the species.