Turriplaca tridentata (Thomsen, 1978) Nicholls, 2012
basionym Pinaciophora tridentata Thomsen (1978)
(synonym Rabdiophrys tridentata Roijackers and Siemensma, 1988)
Diagnosis: Scales of two kinds. Protoplast unknown. Plate-scales circular to oval, 2-3 µm in diameter. Central part of the distal scale surface with a ring of five larger perfora-tions. A single smaller perforation occasionally present in the centre of the scale. Between a rather broad rugose rim and the central ring of perforations is an area perforated by small hexagonally arranged pores. The two plates of the scale are fused peripherally, else-where connected by intercalary material appearing as hexagonally arranged black dots.
Spine-scale c. 3 µm long and c. 0.2 µm wide at the narrowest point. The middle part appears cylindrical. Distally the spine is split into a trifurcate tip (hence the specific epithet). It is supported at the base by short struts that attach to an oval base-plate c. 0.6 µm wide and composed of an oval ring and approximately three cross-beams. Apart from the spaces between the struts, and a few smaller perforations through the trifurcate (tip, the spine-scale appears patternless.
Type location: Dybso Fjord (Denmark). Surface water sample.