The dorsal margin of the valve is convex and the ventral margin is slightly concave. There are somewhat recurved apices that are distinctly rostrate and capitate. The raphe is aparent along the ventral margin of the valve for part of its length. There is a central nodule at the midpoint of the valve or sometimes nearer the ventral margin.The costae ends in the girdle view are capitate. Distinguished by its distinctly capitate rostrate apices.
(Patrick and Reimer 1975).
Type Locality
USA, New England states, New Jersey, Florida, Illinois, Lake Huron, Lake Michigan, Minnesota, and Washington. (Patrick and Reimer 1975).
Synonyms
Epithemia alpestrus W. Smith, Syn. British Diat., vol. 1, pg. 13, pl. 1, fig. 7, 1853.
Epithemia argus var. amphicephala Grun in V.H. Syn. diat. Belgique, pl. 31, fig 19. 1881. (Text p. 140) 1885.
Cystopleura argus var. alpestris Ehr. DeT., Syll. Alg., vol. 2, sect. 2, p. 783. 1892.
(Patrick and Reimer 1975).
Ecological distribution
Found in lakes, ponds, rivers, oozing areas on rock walls and thermal springs. Oligohalobous, prefers water with a salt content less than 500 mg/L. Acidophilous, alkaliphilous and alkalibiontic. (Beaver 1981).
Length is 55 to 62 micrometers (Patrick and Reimer 1975).
Width is 7 to 10 micrometers (Patrick and Reimer 1975).
Costae are about 3 in 10 micrometers (Patrick and Reimer 1975).
Alveoli rows are 11 to 14 in 10 micrometers (Patrick and Reimer 1975).
