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Cymbella excisiformis

Krammer 2002      Category: Asymmetrical biraphid

Cymbella designata


Cymbella hantzschiana

LM scalebar = 10 µm = 80 pixels.


Contributor: Marina Potapova - September 2011
Length Range: 24-34 µm
Width Range: 6.1-7.1 µm
Striae in 10 µm: 9-11 in the center valve, 12-16 at the ends


Valves are strongly dorsiventral, with subrostrate to subcapitate apices. The dorsal margin is strongly arched, whereas the ventral margin is flat or slightly gibbous. The central area is indistinct. One stigma is present at the end of a middle stria. The proximal raphe ends have central pores that curve to the ventral margin. The raphe is lateral, becoming filiform near the distal ends. Striae are slightly radiate. The areolae number 24-28 in 10 μm and are usually distinguishable under LM.

Original Description

Author: Krammer 2002
Length Range: 18-44 µm
Width Range: 6-9 µm
Striae in 10 µm: 9-11 in the center valve, up to 16 at the ends

Original Description

Type locality: South Germany, Ammergebirge, Halblechtal, small brook, epilithic, 25.9.1976, slide 325A IOK.

Valves strongly dorsiventral, linear-lanceolate, dorsal margin strongly convex, ventral margin slightly convex, seldom straight or weakly concave. Sometimes in the centre of the ventral margin of the valve somewhat gibbous or excise. Ends subrostrate, rostrate to subcapitate and narrowly rounded, var. almost without protracted ends. Length range of all varieties 18-44 μm, breadth 6-9 μm, maximal ratio length/breadth 4.2-5.3. Axial area narrow, linear, somewhat curved, central area distinct only in initial and post-initial cells, in other specimen only weakly formed. Raphe slightly ventrally displaced, lateral, becoming filiform near the distal ends and slightly reverse-lateral just towards the proximal ends. Proximal raphe ends slightly rounded; terminal fissures indistinct but, when noted, dorsally deflected. Striae slightly radiate, becoming more radiate near the ends; tiny punc¬tate-lineolate. An isolated stigma is commonly well visible just at the end of the central striae on the ventral side. Striae in the middle portion (dorsal and ventral) 9-11/10 μm, becoming up to 16/10 μm towards the ends, puncta 24-30/10 μm.

Original Images

Cite This Page:
Potapova, M. (2011). Cymbella excisiformis . In Diatoms of the United States. Retrieved May 20, 2018, from

Species: Cymbella excisiformis

Contributor: Marina Potapova

Reviewer: Sarah Spaulding


Krammer, K. (2002). The genus Cymbella. Diatoms of Europe. Diatoms of the European Inland Waters and Comparable Habitats 3: 1-584.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Cymbella excisiformis CAS

NCBI Genbank Taxonomy

Cymbella excisiformis NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 23199

Autecology Discussion