Annuloplatidia annulata (Atkins, 1959)

Figures 44, 45

Platidia annulata Atkins, 1959, p. 133 –142.

Platidia anomioides var. annulata – Brunton & Curry (1979), p. 48.

Annuloplatidia annulata – Zezina (1981).

Description: Shell planoconvex to concavoconvex with dorsal valve almost flat and ventral valve gently convex. Outline subrectangular to transverse oval with very short but pointed beak. Shell surface marked by concentric growth lines. Colour yellowishwhite. Shell matrix endopunctate. Pedicle short. Pedicle foramen large and extending well into posterior part of dorsal valve. Deltidial plates narrow. Short brachidium with an upper transverse band creating a triangular brachial ring supported by and just above median septum. Median septum pillar-like in juveniles, but extending from hinge region to mid-valve length in adults. Setae dense along valve margin and approximately 2/3 of the length of the shell. Maximum shell length 5 mm.

Depth range: Minimum depth range is 1260–2197 m (Lüter 2007).

Substrate: Attached to the coral Enallopsammia rostrata (Atkins 1959) .

Geography: Celtic Sea and the English Channel (Atkins 1959). The species is also reported from the E Pacific (Lüter 2007), but the great distance and oceanographic separation of the populations make it more likely they are two different—though morphologically very similar—species.

Remarks: The shells of all type specimens are dissolved, with only periostracum and soft tissue remaining.