Surirella amphioxys

W.Sm. 1856      Category: Surirelloid
SYNONYM(S): Surirella biseriata f. amphioxys (W.Sm.) Hust. 
REPORTED AS: Surirella moelleriana (Grunow (Hustedt 1930, pg. 435, fig. 842)) 

Stephanodiscus yellowstonensis


Surirella angusta

LM scalebar = 10 µm = 40 pixels.


Contributor: Jonathan English - February 2011
Length Range: 28-48 µm
Width Range: 13.5-17 µm
Striae in 10 µm: 16-20


Valves have a length to width ratio between 2 and 3. The keel is low and no alar wings are visible. Valves are isopolar with cuneate apices and straight, parallel sides. The valve face is strongly undulate (structures termed “porcae”). These porcae appear as rectanglar structures in the LM. Each porca is 2-3 µm wide by 4-5 µm long and is traversed by 3-4 costae, with1-2 costae between each porca. Costae are 16-20 in 10 µm, extending from the margin to the apical axis, where they meet the axial line. Four to five rows of round areolae occur between the costae, visible only in the SEM. A distinct, flat central area occurs about the axial line. Around the valve margin are what appear to be large areolae in the LM, but in the SEM these “areolae” are actually indentations in the valve face corresponding to fibulae in the interior of the valve. Areolae on the surface of the indentations directly beneath the keel penetrate to the mantle. Indentations, or portulae occur on the mantle face, corresponding to those on the valve face.

Original Description

Author: W.Sm. 1856
Length Range: 30.5 µm
Width Range: 12.7 µm
Striae in 10 µm:

Original Description

Surirella amphioxys, n. sp. F. V. linear; V. elliptical-lanceolate, extremities subactute; canaliculi 9 in .001”. Length of frustule .0012”. Breadth of valve .0005”. v.v.

Fresh water. Haverfordwest, August 1855, Mr. Okeden

Original Images

Cite This Page:
English, J. (2011). Surirella amphioxys. In Diatoms of the United States. Retrieved April 26, 2018, from

Species: Surirella amphioxys

Contributor: Jonathan English

Reviewer: Sam Rushforth


Krammer, K. and Lange-Bertalot, H. (1988). Bacillariophyceae. 2. Teil: Bacillariaceae, Epithemiaceae, Surirellaceae. In: Ettl, H., J. Gerloff, H. Heynig and D. Mollenhauer (eds.) Susswasserflora von Mitteleuropa, Band 2/2. Gustav Fisher Verlag, Jena.

Smith, W. (1856). Synopsis of British Diatomaceae. John Van Voorst, London 1856. 2: 107pp., pls. 32-60, 61-62, A-E.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Surirella amphioxys CAS

North American Diatom Ecological Database (NADED)

NADED ID: 65069

Autecology Discussion