Cryptomonad flagellates, cells constantly swimming, occasionally alternating between dissimilar haploid and diploid forms. Haplomorph is slightly compressed with dorsal side convex. The anterior and posterior ends rounded in lateral view. A furrow arises from the posterior of the vestibulum and a sac-like gullet extends posteriorly from the end of the furrow. The periplast consists of inner and outer hexagonal to ovovate plates. The periplastidial compartment contains a single parietal chloroplast (Pigment - Cr-phycoerythrin 545) with a pyrenoid, lacking traversing thylakoids, and a nucleomorph in the posterior of the cell positioned between the pyrenoid and nucleus. The diplomorph is larger and circular in transverse section narrowly elliptic to obovate in lateral view. The vestibulum is situated anteriorly on the ventral surface from which the furrow runs at a slight angle posteriorly for about one third the cell length. A short sac-like gullet is located posterior to the furrow. The periplast consists of an inner sheet and a surface component of an imbricate layer of heptagonal rosette scales The periplastidial compartment has a single parietal chloroplast with a pyrenoid not traversed by thylakoids, and a nucleomorph situated between the nucleus and pyrenoid, Chloroplast contains Cr-phycoerythrin 545. Marine.