Trigonaspis gen. nov. (Prymnesiophyceae) is described on the basis of electron microscopy of shadowcast whole mounts, prepared from water samples collected at Godhavn (West Greenland) in July and August 1977. Members of the genus are small biflagellate coccolithophorids with a short coiling haptonema. The periplast is composed of tower-like coccoliths around the flagellar pole, flattened or slightly elevated coccoliths elsewhere on the cell. Below the coccolith base-plates is a layer of small always unmineralized scales. The coccolith crystallites are triangular plates. Apparently normal cells with unmineralized coccoliths are commonly found. Two species are described, the type species T. diskoensis sp. nov. and T. minutissima sp. nov., both appearing in large numbers in the Greenland cold water samples, but also occurring in Danish coastal waters.
