• Category
  • Length Range
    30.5-48.8 µm
  • Width Range
    15.3-19.3 µm
  • Striae in 10 µm
  • Synonyms
    Anomoeoneis follis (Ehrenb.) Cleve 1895
    Navicula serians var. follis (Ehrenb.) Cleve and J.D.Möller 1879



Valves are rhombic, with broadly rounded apices and an expanded mid valve. The axial area is narrow and straight. The raphe is straight and filiform. The central area is variable in shape and size. It may be round and symmetric, oval or diamond-shaped. Central striae are radiate, except at the ends of the valves where the striae become nearly parallel. There are a few shorter, irregular striae located on either side of the central area. Striae are formed by coarse puncta. Puncta increase in size near the valve margin.


Brachysira follis was present in the surface sediments of Beaver Pond, Holland, Vermont. The surrounding area is largely undeveloped, forested and mountainous. Lakes in this region have low pH, and they are susceptible to acid rain.

Brachysira follis has been reported in the elsewhere in the Northern Hemisphere, specifically in New England (Patrick and Reimer 1966, pg. 377, Pl. 32, Fig. 4.; Camburn and Charles 2000, pg. 22, Pl. 17, Fig. 4). It has also been reported from low-nutrient lakes in Europe (Lange-Bertalot and Moser 1994, pg. 26, Taf. 20, Fig. 1-3) and from Britain (Hartley 1986).

Original Description

222. Navicula Follis, schlauchartiges Schiffchen.

N. Laevis, testula brevi depressa, media parte valde turgida, untroque fine valde constricto rostrate, nec lineata.

Navicule Outre, lisse à carapace courte, deprimée, lateralement très-gonflée au miniew et tres-eranglée aux duex bouts en forme de bec étroit, sans raises longitudinales.

Navicula Follis, Bericht der Akademic d. Wissensch. Zu Berlin, 27. Juni 1836. P 1836. P. 53, 1837. P.44.

Aufenthalt: Im Bergmenhl von Santafiora in Toscana fossil.

Auch dise, der vorigen sehr ähnliche, Art ist noch nicht lebend beobachtet. Sie ist sehr klein. Man muss sich huten, Halbtheile dur jungen Nav. Librile mit ihr zu verwechseln, die nur ein dunnes Ende haben. Die 6 runden Oeffnungen sind beobachtet.—lane 1/102 Linie. Breite etwas mehr als die Langenhalfte.

Eine Abbildung konnte nicht mehr anfgenommen werden. Die N. Follis des Casseler Polirschiefers habe ich doch als besondere Art, N. Crux, und die ven Degernfors als N. Trochus verzeichnet.

  • Basionym
    Navicula follis
  • Author
    Ehrenb. 1836

Original Images

Brachysira Follis Ehrenberg Original Image 1
Brachysira Follis Ehrenberg Original Image 2
Navicula Follis Ehrenberg 1838 Text 1

Cite This Page

Diamond, S. (2018). Brachysira follis. In Diatoms of North America. Retrieved July 19, 2024, from https://diatoms.org/species/brachysira-follis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Brachysira follis 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.