• Category
  • 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

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.

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

Original Images

Cyclotella excisiformis orig illus
Cyclotella excisiformis orig illus 2
Cyclotella excisiformis orig illus 3
Cymbella excisiformis orig descr

Citations & Links

Cite This Page

Potapova, M. (2011). Cymbella excisiformis. In Diatoms of North America. Retrieved June 22, 2018, from https://diatoms.org/species/cymbella_excisiformis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Cymbella excisiformis from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.