Surirella terryi

Ward ex Terry 1907      Category: Surirelloid

REPORTED AS: Surirella terryana (Hustedt 1912 in Schmidt et al. 1874-1959; pl. 280/6-8) | Surirella sp. 1 (Siver et al. 2005; p. 210, pl. 88/5) 

Surirella tenera


Synedra cyclopum

LM scalebar = 10 µm = 20 pixels.


Contributor: Jana Veselá - November 2012
Length Range: 67-176 µm
Width Range: 23–35 µm
Striae in 10 µm: 21–26


Valves are linear with rounded cuneate ends. Valves are typically slightly heteropolar, narrowing towards the foot pole, although some specimens appear isopolar. Valves are slightly, to distinctly, twisted along the apical axis. The valve length is much more variable than the valve width, with the valve length to width ratio ranging from 2.9 to 6.1. Valves are distinctly corrugated. The axial area is narrow and thickened to give the appearance of additional silicification in LM. Porcae are alternate to opposite, within a valve. An alar wing is evident. The raphe is placed in a raised canal and the canal appears about as wide as the fenestrae, which number 16–25 in 100 μm. Fenestrae are typically D-shaped in outline and partially occluded by 7 fenestral bars. The axial area is narrow, elevated to the level of the porcae, without ornamentation or pores. Porcae are ornamented with minute papillae and larger, short, bluntly pointed spines. The spines appear as coarse granulation in LM. Striae are mostly biseriate, sometimes triseriate, often becoming uniseriate towards the median area and radiate at the apices.

Original Description

Author: Ward ex Terry 1907
Length Range: µm
Striae in 10 µm:

Original Description

In five different ponds in Bristol I have found an abundance of a new Surirella, and in one of these ponds it is the predominating form. It is about the size of S. gracilis A. Schm., but not so alate, and with rounded ends, costa distinct, reaching the median line, which is strongly marked; most specimens have a slight spiral twist. It occurs in two types, one greatly elongated. The living frustules are sometimes covered with coarse granulations that do not come off in the acid treatment, but are removed by the soda. Prof. H. L. Smith wrote me “This Surirella is certainly new and much more deserving of a specific name than many others.” Dr. Ward named it Surirella Terryi. I have found this species abundant in one small pond in New Britain and in one at Leete’s Island, but in all other localities known to me it is extremely rare.

Original Images

Cite This Page:
Veselá, J. (2012). Surirella terryi. In Diatoms of the United States. Retrieved April 23, 2018, from

Species: Surirella terryi

Contributor: Jana Veselá

Reviewer: Rex Lowe


Schmidt, A. (-). (1874-1959). Atlas der Diatomaceen-Kunde, von Adolf Schmidt, continued by Martin Schmidt, Friedrich Fricke, Heinrich Heiden, Otto Muller, Friedrich Hustedt. Reprint 1984, Koeltz Scientific Books, Konigstein, 480 plates.

Siver, P.A., Hamilton, P.B., Stachura-Suchoples, K. and Kociolek, J.P. (2005). Diatoms of North America. The Freshwater Flora of Cape Cod. Iconographia Diatomologica 14: 1-463.

Tempère, J. and Peragallo, H. (1907). Diatomées du Monde entier: Collection Tempère et Peragallo, 2nd edition. Text. Chez J. Tempère, villa Andrée-Lucie à Arcachon (Gironde). 480pp.

Terry, W.A. (1907). A partial list of Connecticut diatoms with some account of their distribution in certain parts of the state. Rhodora 104: 125-140.

Terry, W.A. (1908). Additional list of Connecticut diatoms. Rhodora 10: 179-184.

Veselá, J., Johansen, J.R. and Potapova, M. (2013). Surirella terryi and S. cruciata: two rare diatoms in North America. Diatom Research . 10.1080/0269249X.2013.853697

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Surirella terryi CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Surirella terryi was observed only in 11 freshwater lakes and small streams in coastal areas of the northeastern U.S. (CT, DE, ME, NJ, PA) and Washington state, all within 60 km of the ocean shore. It was fairly abundant in the type material (Ice Pond, New Britain, Connecticut) and Lee’s Pond in Bristol (ca. 15 km west of New Britain), where hundreds of valves of S. terryi were present. In all other slides S. terryi was present in much smaller numbers (n ≤ 44 valves). An additional record of the taxon is given in Siver et al. (2005) as Surirella sp. 1. They found the species in two ponds on the Cape Cod peninsula in Massachusetts and reported it as being rare.


Initial cell

Credit/Source: Cromwell Brook, Acadia National Park, ME.