(Haeckel)
Diagnosis: Shell ovoid, slightly compressed, with one large conical spine and sometimes a few smaller spines on aboral pole, half as long as radius. Peristome short and wide, collar-shaped, about twice as wide as long, half as long as radius, obliquely inclined over mouth, with 2 divergent straight teeth, conical and longer than shell radius. Base of each tooth with large ovate pore in wall of peristome.
Diameter: 0.08-0.10 mm.