Chain-forming species with anterioposterior compression. Epitheca has shoulders and the cingulum has curtain fins. Hypotheca has prominent sulcal lists that appear as spines. The 1' is without a vp and the APC is diagnostic. Toxic.
Remarks: this species can be distinguished from its nearest relatives by cell shape, no vp, Po touching the 1', and the APC.
Distribution: cold water species, coastal, Pacific Ocean of North America, south and central Chile, southern Argentina, western South Africa, Japan, Kamchatka peninsula in the Soviet Union, Tasmania, and south of Australia. Also found in southern California in Monterey Bay in 1991.