Description: Shells very large; adult specimens 94 to 109
mm in height (Table 2), usually comprising six whorls; shell
very thick and solid, consisting of two differently shaped
parts. First 3 to 3.5 whorls very low-trochospiral; apical
angle ca. 130°; apex distinct but blunt; umbilicus wide, accounting
for ca. 15% of shell width. Adapical part of whorls
slightly flattened; partly ornamented with minute spiral to
tangential furrows. Shoulder ornamented with thick, wellrounded
band of hollow, flattened, rounded-lobate spines
(7-8 spines on last whorl of first ontogenetic stage), set off
from adapical shell portion by a shallow but distinct furrow;
ornamentation resulting in a blossom-like shape in upside
view (Fig. 5). Growth lines distinct but smooth. Suture distinct.
Aperture almost circular. Transition to second growth
stage smooth and gradual, but relatively rapid, within ca 10
mm of shell growth; shift of curling axis achieved by disproportionate
insertion of new shell material, with a maximum
at the outer side of whorl; curling axis shifting for ca.
10°. Second shell portion consisting of 2.5 whorls; highconical;
apical angle ca. 45°. Adapical portion of whorls
steeply inclined, almost straight; whorl centre ornamented
with a single broad, blunt carina; carina ornamented with
low, densely spaced spines (> 25 spines on body whorl).
Spines emerging from regions above and below carina;
widely open in growth direction, with an arcuate cross-section.
Abapical whorl portion slightly rounded. Suture deep.
Minute umbilicus covered by inner lip. Aperture rounded to
slightly tear-shaped.