Alvania Risso 1826

Alvania sp. B

Fig. 26C

Material. MGUH 33165 and an external mould in the uncatalogued collections of the Natural History Museum of Denmark.

Occurrence. The lower Danian ‘dead layer’ in Vokslev Quarry, Northern Jutland.

Description. Protoconch obtusely conical with 2 ¼ to 2 ½ convex whorls. Whorls seemingly smooth, but could have been weakly postulate. Protoconch height between 0.3 and 0.35 mm, while the width reaches 0.55 mm.

Shell high trochiform with weakly convex whorls separated by fairly distinct suture. Transition to base at periphery moderately sharp. Aperture not preserved.

Teleoconch sculpture dominated by about 22 to 25 opisthocyrt transverse ribs per whorl. Ribs reaching down to periphery before fading out. Transverse ribs crossed by generally weaker spiral ribs; adapical one much stronger than succeeding ones, carrying small beads representing adapical part of transverse ribs. Spiral ribs increasing in strength at and just abapically of periphery with up to five moderately distinct spirals on adapical part of base.

Measurements. MGUH 33165 is 0.8 mm wide, consisting of the last protoconch whorl and the succeeding teleoconch whorl.

Remarks. Alvania sp. B resembles the late Maastrichtian A. sp. A described above, but differs by the stronger spiral sculpture and the more opisthocline nature of the transverse ribs.