Thyasira equalis

Thyasira equalis (Verrill & Bush, 1898) Fig. 13 Following his investigations in the USNM, Ockelmann began to apply some of Verrill & Bush’s names to European specimens. The first of these was to identify a species from the Fladen Ground in the North Sea as T. equalis following communications with Alistair McIntyre (McIntyre 1961). However, T. equalis was not included in the British fauna by Tebble (1966) but was listed by Bowden & Heppell (1968). It appears in the Norwegian literature in 1975 (Lande 1975), but the first figures of European specimens were published by Payne & Allen (1991), and illustrations of specimens from the North Sea are in Oliver & Killeen (2002). Comparisons of the shells from NE America, the North Sea and northern Norway show that they share the same characters and in particular the micro-sculpture of the prodissoconch. This has the characteristic “menorah” pattern (Fig. 22A) which Ockelmann did not see. Ockelmann’s map (Fig. 13) shows a discontinuous distribution with a western Atlantic range from New England northwards into the Labrador Sea but absent from the entire east of Greenland. In the east, it ranges from the North Sea into the Kattegat and all along the Norwegian coast into the Barents Sea.