Craticula Grunow (1868)

Grunow, 1868. Reise Fregatta "Novara" Bot. 1 (i): 20

Cells usually lanceolate to linear lanceolate in valve view with subrostrate to rostrate apices, narrowly rectangular in girdle view. Live cells solitary, with two plate-like chloroplasts lying along the girdle, and extending slightly under the valve face. Often with 2 conspicuous droplets between the central cytoplasmic bridge and the cell apices. Valves with central raphe slits, continuing over the apices, slightly expanded at centre. Striae often more or less parallel, uniseriate with fine regular pores. Valves may appear as if transected also by longitudinal striae. Few girdle bands, each with a single row of pores.

Formerly included in Navicula sensu lato.


M.G. Kelly, H. Bennion, E.J. Cox, B. Goldsmith, J. Jamieson, S. Juggins D.G. Mann & R.J. Telford (2005). Common freshwater diatoms of Britain and Ireland: an interactive key. Environment Agency, Bristol.


Species described:-

Craticula cuspidata (Kützing) D. Mann


Craticula cuspidata (Kützing) D. Mann

Craticula cuspidata (Kützing) D. Mann 104.5u x 27u. Striae 13.85 in 10u.
Craticula cuspidata (Kützing) D. Mann 104.5u x 27u. Striae 13.85 in 10u.

Valves rhombic-lanceolate to broadly rhomboidal, tapering to narrowly rounded apices. Striae parallel throughout the valve, resolvable into fine pores along the striae. Raphe slits straight, lying in a slightly thickened area of silica which widens slightly around the central raphe endings and at the poles where it is highly refractive. Central raphe endings slightly expanded, polar fissures curved to one side.


Alkaliphilous - mainly occurring at pH > 7
Salinity - Fresh to brackish

Tolerant of moderate to heavy pollution