Cylichnoides sp. 1.

Figs 4M; 5J–O

Material studied. Chukchi Sea: Wrangel Isl., icebreaker «Fyodor Litke», 01.IX.1929, station 44 – 1 specimen, collected by P. V. Ushakov.

D e s c r i p t i o n. This shell has an almost straight columellar margin (Fig. 4M), very fine spiral sculpture, pale yellow periostracum and unusual rachidians. Spiral sculpture (Fig. 5O) consists of the weak straight striae equally close over the whole shell, mostly at regular distances from each other. These striae alternate with two more weak striae, which can be seen more clearly at the electron microscopy images. The height of the shell is 7.8 mm. Radula (Fig. 5J–N) has formula 10x2:1:1:1:2, lateral teeth with 20–24 regularly spaced curved denticles, which descend to the base of the tooth. Rachidian teeth equipped with the long curved denticles tapering with 1–4 filiform ends. Cutting edge is a simple rounded form. Lateral edges not rolled.

N o t e s. The species differs from other species of Cylichnoides in shell sculpture and rachidian teeth morphology. Rachidian tooth is equipped with long curved denticles tapering with 1–4 thread ends.