Placoneis amphibola

(Cleve) E.J.Cox 2003      Category: Symmetrical biraphid
BASIONYM: Navicula amphibola Cleve 1891
SYNONYM(S): Navicula punctata var. asymmetrica Lagerst. | Navicula gastrum var? styriaca Grunow 

Placoneis abiskoensis


Placoneis anglophila

LM scalebar = 10 µm = 40 pixels.


Contributor: Mark Edlund | David R.L. Burge - June 2017
Length Range: 39-66 µm
Width Range: 21.6-25.6 µm
Striae in 10 µm: 5.5-8.5


Valves are elliptic and curved so that they are slightly asymmetric to the apical axis. In smaller specimens, the valve margins are parallel. Apices are rostrate and rounded. The axial areal is narrow. The central area is bowtie-shaped and bounded by 3-4 short striae of variable length. Raphe branches are both undulate and lateral. The proximal raphe ends are expanded and the terminal raphe ends are deflected toward the primary side of the valve. Striae are radiate and curved toward the valve center throughout. Striae are distinctly punctate, with an areola density of 10-18 in 10 µm.

Cleve (1891) proposed this species based on three syntypes that were previously recognized as varieties: Navicula punctata var. asymmetrica Lagerstedt (1873, p. 29; pl. 2, fig. 7), N. gastrum var? styriaca Grunow (1882, p. 144; pl. 30, fig. 50), and N. gastrum var? styriaca Grunow (Grunow 1884, pl. I, fig. 35). As such, this species awaits lectotypification.

Original Description

Basionym: Navicula amphibola
Author: Cleve 1891
Length Range: µm
Striae in 10 µm:

Original Description

N. amphibola Cl. — N. punctata var asymmetrica Lagst. II, 7. — N. gastrum var? styriaca Grun. E. Öst. Ung. XXX, 50, 51, F. Jos. Land, I., 35. Foss. Lk. 93. This form seems to be a good species, for which I should have liked to have proposed the name N. styriaca, had not this name been given to another species.

Original Images

Cite This Page:
Edlund, M., and Burge, D. (2017). Placoneis amphibola. In Diatoms of the United States. Retrieved April 23, 2018, from

Species: Placoneis amphibola

Contributor: Mark Edlund | David R.L. Burge

Reviewer: Sarah Spaulding


Cleve, P.T. (1891). The Diatoms of Finland. Actas Societas Pro Fauna et Flora Fennica 8 (2): 1-68.

Cox, E.J. (2003). Placoneis Mereschkowsky revisited: resolution of several typification and nomenclatural problems, including the generitype. Bot. J. Linn. Soc. 141: 53–83. 10.1046/j.1095-8339.2003.00115.x

Foged, N. (1981). Diatoms in Alaska. Bibliotheca Phycologica, Band 53, J. Cramer, Vaduz, 317 pp.

Grunow, A. (1882). Beiträge zur Kenntniss der Fossilen Diatomeen Österreich-Ungarns. In: Beiträge zur Paläontologie Österreich-Ungarns und des Orients, (E. von Mojsisovics und N. Neumahr, eds). Wien. 2(4):136-159, pls. XXIX-XXX.

Grunow, A. (1884). Die Diatomeen von Franz Josefs-Land. Mathematisch-Naturwissenschaftliche Classe, Wien 48: 53-112, 5 pls.

Lagerstedt, N.G.W. (1873). Sötvattens-Diatomaceer från Spetsbergen och Beeren Eiland. Bihang till Kongliga Svenska Vetenskaps-Akademiens Handlingar 1 (14): 1-52, 2 pls.

Patrick, R.M. and Freese, L.R. (1961). Diatoms (Bacillariophyceae) from Northern Alaska. Proceedings of the Academy of Natural Sciences of Philadelphia 112(6):129-293.

Patrick, R.M. and Reimer, C.W. (1966). The Diatoms of the United States exclusive of Alaska and Hawaii, V. 1. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Stevenson, R.J. and Stoermer, E.F. (1978). Diatoms from the Great Lakes. II. Some rare or poorly known species of the genus Navicula. Journal of Great Lakes Research 4: 178-185.

Stoermer, E.F. (1964). Notes on Iowa diatoms. VII. Rare and little known diatoms from Iowa. Iowa Academy of Sciences 71: 55-66, 5 pls.

Stoermer, E.F. (1980). Characteristics of benthic algal communities in the upper Great Lakes. U.S. Environmental Protection Agency, Ecological Research Series, EPA 600/3-80-073. Environmental Research Laboratory, Duluth, Minnesota. 72 pp.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA

California Academy of Sciences (CAS)

Placoneis amphibola CAS

North American Diatom Ecological Database (NADED)

NADED ID: 46474

Autecology Discussion

Placoneis amphibola has been reported from a number of locations in North America, although it is typically rare in abundance. It has been reported from Connecticut, Nebraska, Wyoming, Washington, Oregon, and California (Patrick and Reimer 1966). Specimens from West Lake Okoboji, Iowa have been documented (Stoermer 1964), while Foged (1981) reports it from small ponds in Alaska.

A number of forms and varieties have been noted, including Navicula amphibola fo. alaskensis Foged, Navicula amphibola fo. rectangularis Foged (Foged 1981) and Navicula amphibola var. arctica Patrick & Freese (Patrick and Freese 1961). Yet another variety, Navicula amphibola var. perrieri M. Perag. & Héribaud, has been reported from northern Lake Michigan (Stevenson & Stoermer 1978, Stoermer 1980).

The population illustrated on this page was found to be sympatric with a larger, and undetermined, Placoneis with parallel sides, capitate apices and coarse striae and areolae. These larger Placoneis are discontinuous in a size-shape series to the nominate form of P. amphibola.


Unidentified Placoneis taxon found to be sympatric with P. amphibola.

Credit/Source: Mark Edlund, Iowa Lakeside Lab Collection ILL 2017-08, Minnesota Landscape Arboretum