Corliss & Snyder (1986: 41, fig. 2)
Petz et al. (1995: 32)
In vivo (80–) 180–260 (–700) × (30–) 65–120 (–290) µm. Body bottle- to club-shaped, contractile, always posteriorly pointed; caudal constriction 30–40 µm long; pharyngeal plug conspicuous; broad head distinct from inconspicuous neck. Cytoplasm often reddish brown (due to digested diatoms?), containing deep red, rarely yellow-green, food vacuoles rendering specimens dark reddish brown to almost black, rarely orange or greenish at low magnification. Cortical granules ruby-red (rarely almost colourless), in interkinetal rows. Somatic kineties 14–49 on body, c. 35 ciliary rows on head. Brosse formed by 1–few dikinetids at anterior end of each somatic kinety. Extrusomes c. 22 µm long, rod-shaped. Macronucleus long, irregularly spiralled; micronuclei 1–3 (always 3?). Contractile vacuole subterminal. Movement: rather slow, short distances back and forth between detritus, rotates about long axis when swimming.
Ross Sea, in the region 65.28°–76.02°S and 164.12°E–134.85°W, in sea-ice and on the sea floor (Petz, unpublished data; Petz & Valbonesi, unpublished data); Weddell Sea (Corliss & Snyder, 1986; Petz et al., 1995).