Haeckel
Diagnosis: Shell lenticular, strongly compressed, ratio of longitudinal to sagittal to lateral diameters = 10:9:3, sagittal perimeter elliptical, cinctural and frontal perimeters spindle-shaped. Borders of two boat-shaped valves smooth in oral and aboral thirds, dentate in middle fourth, about 40-44 very slender equal teeth on one lateral edge of each valve. In half frontal perimeter 64-68 pores, in half sagittal perimeter 70-80 pores, in half equator 44-48 pores. Ventral and dorsal pores linear, 3 to 4 times as long as circular, lateral pores.
Length: 0.6-0.8 mm.