Daugbjerg (2000: 161, figs 2-48)
Daugbjerg et al. (2000: 199–209)
[after Daugbjerg et al. (2000)] Cells 8–12 µm long, 6–8 µm diameter, with slightly convex sides. Body scales of 4 types: an outer rather loose layer of crown scales, a middle layer of closely fitting box scales, an inner layer of small footprint scales, and an underlayer of minute square scales around the flagellar pit. Crown scales c. 300 nm across the base; scale base with 4 ribs in a cross supporting a central strut that connects distally with 4 curved arms arising from the scale base edges. Box scales square, c. 300 nm on each side, c. 80 nm high, ornamented with parallel striations and scattered perforations. Footprint scales 70 nm long, 20 nm wide, dispersed between the box scales. Flagella thin, slightly longer than the cell body, with an outer layer of limulus scales and an underlying rows of pentagonal scales and 2 rows of hair-shaped scales; limulus scales c. 313 nm long (including apical spine); pentagonal scales c. 40 nm diameter; hair scales c. 1.3 µm long. Cells with a single cup-shaped chloroplast lobed anteriorly. Two eyespots in adjacent chloroplast lobes about halfway down the cell.
Type locality, Weddell Sea, 60°S 49°W (Daugbjerg, 2000); Ross Sea (Daugbjerg et al., 2000).
Sym & Pienaar (1993) discussed the diagnostic characteristics of the green flagellate Pyramimonas. Cells have either 4 or 8 flagella of equal length emerging from the anterior end of the cell. Up to 7 types of non-mineralised scales cover the cell body and the flagella, and these scales are diagnostic at the species level.
Cysts spherical, c. 10 µm diameter, with a uniform covering of a single scale type not seen on the vegetative (flagellate) cell; scales spine-like, c. 60 nm high; scale base-plate similar to that of vegetative cell box scales, 150 nm wide, but with a horn-like elongation 300–500 nm high with a terminal hook on each of the 4 corners.