Compare

Ulnaria delicatissima var. angustissima has longer and more tapering valves with a higher stria density (Length: >200 µm, Stria density 13-14 in 10 µm; Patrick & Reimer, 1966). Ulnaria ulna has wider valves (6 to 8 µm, Lange-Bertalot & Ulrich, 2014) and is usually lacking a central area. Ulnaria acus, Fragilaria saxoplanktonica, and Fragilaria grunowii valves are more strongly tapering, with a higher striae density (11 to 13,12 to 15, and 23 to 28 in 10 µm, respectively; Lange-Bertalot & Ulrich, 2014).

LM scalebar = 10 µm
Ulnaria delicatissima LM15 Ulnaria delicatissima LM16 Ulnaria delicatissima LM18 Ulnaria delicatissima LM19 Ulnaria delicatissima LM20 Ulnaria delicatissima LM21 Ulnaria delicatissima LM22
Length Range
158.2-262 µm
Width Range
5 µm
Striae in 10 µm
10-11

Also compare to

Ulnaria delicatissima var. angustissima

(Grunow) Aboal and Silva

Ulnaria ulna

(Nitzsch) Compère

Ulnaria acus

(Kütz.) Aboal

Fragilaria saxoplanktonica

Lange-Bert. and Ulrich

Fragilaria grunowii

Lange-Bert. and Ulrich