Marshallora cf. adversa ( Montagu, 1803 )

Marshallora cf. adversa ( Montagu, 1803) View in CoL ( Fig. 5J View FIG 1-J View FIG 3 View FIG )

cf. Murex adversus Montagu, 1803: 271 .

cf. Triforis perversa var. adversa – Harmer 1918: 425, pl. 41 fig. 25.

cf. Mashallora cf. adversa – Van Dingenen et al. 2016: 162, pl. 14 figs 7, 8.

MATERIAL AND DIMENSIONS. — Maximum height 5.8 mm (incomplete), width 3.2 mm.— RGM.1364975 (3), leg. ACJ ; RGM.1365280 (1), leg. AWJ .

SPECIES CHARACTERISATION. — Apex lacking on all material. Overall shell is slightly spindle shaped. Adult whorls separated by superficial suture; sculpture of three spiral ribs, middle rib slightly stronger than other ribs; numerous weak, prosocline ribs, with rounded tubercles developed at intersections; on last whorl the fourth basal rib is smooth to slightly knobbed and a fifth rib in one specimen is smooth reminiscent of a recent Canarian Island morph of this species (H. Bakker, pers. comm.). The Selsoif specimens are large for this species.

DISTRIBUTION. — Lower Pleistocene: Atlantic, Selsoif, NW France (this paper). Today Marshallora adversa is distributed in the NE Atlantic from Scandinavia to the Canaries and in the entire Mediterranean ( Bouchet 1985).

REMARKS The three extant West European species Marshallora adversa ( Montagu, 1803) , Cheirodonta pallescens ( Jeffreys, 1867) and Similiphora similior (Bouchet & Guillemot, 1978) are almost indistinguishable on shell characters alone ( Marquet 1996). The protoconch and position of appearance of the cords on early whorls is required to make a definitive attribution.