Petz, Song & Wilbert (1995: 79, figs 23, 58)
In vivo 190–300 × 55–70 µm. Body usually lanceolate, dorsoventrally flattened, appears dark at low magnification and brown to green, sometimes reddish at higher magnifications; pigment spot not observed. Somatic kineties 93–129, forming a distinct suture on ventral side, which also extends a short distance onto dorsal side; 4 or 5 comparatively long vestibular kineties overlap 3 peniculi; postoral kineties 4 or 5. Extrusomes densely spaced beneath pellicle; resting stages fusiform, in vivo c. 10 µm long, the ejected ones to 56 µm long and rod-shaped. Macronucleus 1; micronuclei (1 or) 2, reniform. Contractile vacuole in posterior 16–20% of body. Silverline system quadrangular. Movement: slowly gliding.
Ross Sea (Petz, unpublished data); Weddell Sea (Petz et al., 1995).