Corliss & Snyder (1986: 44, fig. 7)
Petz et al. (1995: 172)
In vivo 45–55 × 30–40 µm. Body D-shaped, widest at or behind mid-body, posteriorly on left with a distinct thorn-like projection (prostomial spur) associated with indentation of cell, sometimes right border of indentation also spur-like, with 4 conspicuous dorsal ridges, dorsoventrally flattened. Cirri: 7 or 8 frontoventral, 5 or 6 transverse. Dorsal kineties 4, each with 4–10 dikinetids. Frontal membranelles 3; adoral membranelles c. 9–12. Macronucleus horseshoe-shaped; micronucleus 1. Contractile vacuole 1. Movement: slowly crawling, rotating about main body axis when swimming.
Ross Sea, in the region 66.00°–74.03°S and 134.85°–165.02°W, in sea-ice (Petz, unpublished data); Bellingshausen Sea (Klöser, 1990); Weddell Sea (Corliss & Snyder, 1986; Petz et al., 1995).