Liostomia

Liostomia sp.

Fig. 17 p–r

Diagnostic characters. Conical-ovate shell; whorls weakly convex; drop-shaped aperture; small umbilical chink; outer surface with sinuous growth lines only. Protoconch: heterostrophic, coaxially immersed (intorted); about 1.25 visible whorls; diameter about 300 µm; surface smooth; transition to the teleoconch marked by a simple, thin lip.

Remarks. The present specimens are attributed to the genus Liostomia G. O. Sars, 1878 on the basis of the “ type C” protoconch (sensu Van Aartsen 1987) and the absence of a columellar tooth or fold. Liostomia sp. differs from the related L. clavula (Lovén, 1846) and L. afzelii Warén, 1991 [b], primarily in terms of shell shape (it is distinctly conical) and overall dimensions (it needs one more whorl to reach a comparable heigth). The northern Atlantic L. eburnea (Stimpson, 1851) is also similar, but it has slenderer shell and orthocline growth lines.

Occurrence. Box-corer sample BC72 (2 specimens); cores BC04 (1), BC05 (1). Maximum height: 2.5 mm.

Distribution and habitat. Liostomia species are parasites (host unknown; cf. Høisaeter 2014); they occur in both the northern Atlantic and the Mediterranean, from infralittoral to bathyal depths (Van Aartsen 1987; Van Aartsen et al. 1998; Schander et al. 2003; Petersen 2004; Høisaeter 2009).