Meridion anceps

(Ehrenberg) D.M. Williams 1985      Category: Araphid
BASIONYM: Fragilaria anceps Ehrenberg 1843
SYNONYM(S): Diatoma anceps (Ehrenberg) Kirchner 1878 

Melosira varians


Meridion circulare

LM scalebar = 10 µm = 80 pixels.


Contributor: Ian Bishop - May 2015
Length Range: 10.4-45.8 µm
Width Range: 5.2-7.0 µm
Striae in 10 µm: 18-23


Valves apically and transapically symmetrical; linear with capitate ends. Small valves may be more elliptical with less capitate ends than larger valves. Valves possess both primary and secondary costae, which measure 3.3-4.9 in 10 µm. Striae are visible in LM but individual areolae cannot be observed. The sternum is central and well-defined. Each valve has a single, sub-apical rimoportula.

Original Description

Basionym: Fragilaria anceps
Author: Ehrenberg 1843
Length Range: µm
Striae in 10 µm:

Original Description

F? anceps, parva linearis testulis a latere laxe striatis, apicibus, constrictis obtusis subcapitatis. Gomphonema Pupulae affinis.

Original Images

Cite This Page:
Bishop, I. (2015). Meridion anceps. In Diatoms of the United States. Retrieved July 06, 2015, from

Species: Meridion anceps

Contributor: Ian Bishop

Reviewer: Rex Lowe


Ehrenberg, C.G. (1843). Verbreitung und Einfluß des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin, 1841: 291-445, 4 Tafel.

Williams, D.M. (1985). Morphology, taxonomy and inter-relationships of the ribbed araphid diatoms from the genera Diatoma and Meridion (Diatomaceae: Bacillariophyta). Bibliotheca Diatomologica 8: 1-228.

Williams, D.M. (1990). Cladistic analysis of some freshwater araphid diatoms (Bacillariophyta) with particular reference to Diatoma and Meridion. Plant Systematics and Evolution 171: 1615-6110.

Links & ID's

Index Nominum Algarum (INA)


California Academy of Sciences (CAS)

Meridion anceps CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Meridion anceps is widely distributed across North America, notably in the western United States. It can be found in aerophilic zones, wet walls, small creeks, larger rivers. It is common in submerged mosses and liverworts and co-occurs with several species in the Meridion, Diatoma, Tabellaria, and Tetracylus genera.


Distribution of D anceps in the continental U.S. rivers sampled for the National Water Quality Assessment program. (Retrieved 08 May 2015)

Credit/Source: USGS BioData

Distribution of D anceps in the Alaskan rivers sampled for the National Water Quality Assessment program. (Retrieved 08 May 2015)

Credit/Source: USGS BioData