• Polykrikos schwarzii: Kofoid (1907)

The cell is athecate,  from small to medium dimensions, oval in shape, cells longer than they are wide. Cells join together to form pseudo-colonies made up of 4 zooids and with two nuclei per zooid. The cell surface is covered in crests, and the cingulum is in a median position. The cytoplasm does not contain chloroplasts.

Cosmopolitan, typical of temperate to tropical coastal waters.

Distribution: as Polykrikos schwarzii: Asia: Japan (Nagai, Matsuyama, Takayama & Kotani, 2002).

As Polykrikos kofoidii: Europe: Great Britain (Parke & Dixon 1976); North America: British Columbia (Hoppenrath & Leander 2007); Asia: Japan (Nagai, Matsuyama, Takayama & Kotani 2002), Korea (Jeong, et al. 2002).

Check-list of British marine algae - third revision., Journal of the Marine Biological Association of the United Kingdom 56, Parke M., Dixon P.S., 1976, 527-594.

Thalassiosira species (Bacillariophyceae, Thalassiosirales) in the North Sea at Helgoland (Germand Bight) and Sylt (North Frisian Wadden Sea) - a first approach to assessing diversity., European Journal of Phycology 42:, Hoppenrath M., Beszteri B., Drebes G., Halliger H., Van Beusekom J.E.E., Janisch S., Wiltshire K.H., 2007, 271-288

NaOCl produced by electrolysis of natural seawater as a potential method to control marine red-tide dinoflagellates., Phycologia 41:, Jeong H.J., Kim H.R., Kim K.L., Kim K.Y., Park K.H., Kim S.T., Yoo Y.D., Song J.Y., Kim J.S., Seong K.A., Yih W.H., Pae S.J., Lee C.H., Huh M.D., Lee S.H., 2002, 643-656

Morphology of Polykrikos kofoidii and P. schwartzii (Dinophyceae, Polykrikaceae) cysts obtained in culture., Phycologia 41:, Nagai S., Matsuyama Y., Takayama H., Kotani Y., 2002, 319-327