Haeckel
Diagnosis: Shell subcircular in outline, lenticular, strongly compressed on both sides. Sagittal perimeter nearly circular, frontal and cinctural perimeters spindle-shaped. Borders of two boat-shaped valves smooth in 0.4 of oral part, and in 0.1 of aboral part, remaining 0.5 middle part strongly dentate, with about 25 straight, slender teeth on each side of one valve, increasing in size from aboral towards oral pole. In the half lateral perimeter of the shell (along the right and left borders of each valve) 60-65 pores, in the half sagittal perimeter (along the keel of each valve) 80-85 pores, in half equator 60-65 pores.
Diameter: 0.53-0.75 mm.