Caulostrepsis taeniola Clarke, 1908

Diagnosis.—Gallery cylindrical, bent in a narrow U-form which is sometimes enlarged in the shape of a tongue. The inward facing margins of the limbs are always interconnected by a distinct vane. Limbs closer or partially fused towards the apertural extremity. Transverse section dumbbell-shaped, aperture 8-shaped (cited from Bromley and D’Alessandro 1983).

Remarks.—The presence of the roof at the end of some depressions suggests that the roof was more extensive but was broken or collapsed. Caulostrepsis taeniola is the most common ichnospecies of Caulostrepsis. It is produced mainly by the spionid polychaete Polydora ciliata (Johnston, 1838), which is common on mid-latitude Atlantic coasts (Radwański 1969, and references therein), mostly up to a depth of 25 m (Boekschoten 1966). Polydora lives in different substrates and conditions; it can also live in polar regions (Hanken et al. 2012) and in brackish waters (D’Andrea et al. 1996; Murina 1997).

Description — The figured specimen is a U-shaped boring having cylindrical limbs separated by a vane at its distal end and constricting to an axial depression towards the proximal extremity. The limbs and vane are only pronounced on the side facing the substrate (inward-
facing). Only a slight impression of the limbs arid vane are preserved on the outward-facing margin. The diameter of the limbs decreases to approximately 0.3 mm at the vertex, but otherwise remains constant at 0.4 mm. The structure, 4 mm in length, is curved close to the
vertex and slightly twisted towards the aperture. The aperture is concealed.