(Lovén, 1946)
Description:
The shell is distinctively triangular in outline, with its widest part anteriorly and may be wider than long. It reaches a maximum length of approx. 37 mm. A broad anterior sulcation is present. The external surfaces of the valves are smooth except for concentric growth lines. The shell is endopunctate. It is white or yellowish in colour. The pedicle foramen is circular, and the deltidial plates unite medianly.
Internal:
Medium septum long and prominent; loop long, simple, with a wide hooded, transverse band. Lophophore with long lateral lobes and a median spiral (D. septigera internal).
Habitat:
A deep water species.
Distribution:
Scotland, North Sea, and down the western continental edge; northern Norway to the Canary Islands.