Amphora bicapitata

M.H.Hohn and Hellerman 1966      Category: Asymmetrical biraphid

REPORTED AS: Halamphora acutiuscula (Levkov 2009, Pl. 96, Figs. 10-18; Pl. 109, Figs. 36-44; Pl. 234, Figs. 1-4) 

Amphipleura pellucida


Amphora calumetica

LM scalebar = 10 µm = 80 pixels.


Contributor: Ian Bishop - March 2017
Length Range: 24-29 µm
Width Range: 5.2-5.5 µm
Striae in 10 µm: 20-22 off-center on the dorsal side, 22-23 off-center on ventral side


Valves are dorsiventral, with a convex dorsal margin and a linear to weakly convex ventral margin. Apices are protracted, capitate, and deflected ventrally. Dorsal striae are coarse, especially at mid-valve and toward the dorsal margin; areolae measure 18-20 in 10 µm. Ventral striae are short, most so at mid-valve. Axial area is minimal on the dorsal side and expanded ventrally. Raphe is straight, with dorsally deflected proximal ends. Central dorsal striae have a darker quality in LM due to an underlying siliceous plate. Under SEM, striae are biseriate nearest the raphe.

It should be noted that this taxon (or something very similar to it) has been reported as Halamphora acutiuscula (Kützing) Levkov (see above REPORTED AS:). In 2009, Levkov transferred Amphora acutiuscula Kützing to Halamphora, providing observations based on LM and SEM micrographs from Baltic Sea populations (Pl. 96, Figs. 10-18; Pl. 109, Figs. 36-44; Pl. 234, Figs. 1-4). He also revisited Kützing’s original Amphora acutiuscula material and published four LM images (Pl. 265, Figs. 12-15). It is this author’s opinion that the non-type populations Levkov imaged are not conspecific with H. acutiuscula sensu Kützing, but instead bear strong resemblance to A. bicapitata Hohn & Hellerman (1966). The holotype of A. bicapitata was recently revisited and imaged (Desianti et al. 2015). No specimens were found, however, in SEM preparations.

Original Description

Author: M.H.Hohn and Hellerman 1966
Length Range: 24.9 µm
Width Range: 5.2 µm
Striae in 10 µm: 20-21 dorsally, 22-23 ventrally

Original Description

Valva cum marginibus convexis, apicibus capitatis asimiliter; longitudo 24.9 μ; latitudo 5.2 μ; area axiali angustissima dorsualiter, lata ventraliter; raphe paene directa; area media dilatata rectangulate dorsualiter; striis dorsualibus punctatis, radiatis leniter, praecisis ad mediam partem 20-21/10 μ; striis ventralibus, brevibus teneris 22-23/10 μ.

Valve with convex margins, ends asymmetrically capitate; length 24.9 μ;width 5.2 μ; axial area very narrow dorsally, wide ventrally. Raphe nearly straight; central area rectangularly expanded dorsally; dorsal striae punctate, slightly radiate, shortened at center 20-21/10 μ; ventral striae short, delicate, 22-23/10 μ.

This taxon is similar to Amphora fontinalis Hust. (Arch. Hydrob. Suppl. 15: 414, pl. 24, fig. 4, 5, 1938) but differs in that the ventral striae are not interrupted as they are in A. fontinalis. Also a sulcus-type structure on the dorsal side of the valve is not evident as it is in A. fontinalis.

Specimen illustrated: G.C. 44892, type. Type locality: Middle River, Baltimore Co., Md. Distribution: Type locality.

Original Images

Cite This Page:
Bishop, I. (2017). Amphora bicapitata. In Diatoms of the United States. Retrieved April 25, 2018, from

Species: Amphora bicapitata

Contributor: Ian Bishop

Reviewer: Zlatko Levkov


Desianti, N., Potapova, M. and Beals, J. (2015). Examination of the type materials of diatoms described by Hohn and Hellerman from the Atlantic Coast of the USA. Diatom Research. 10.1080/0269249X.2014.1000020

Hohn, M.H. and Hellerman, J. (1966). New diatoms from the Lewes-Rehoboth Canal, Delaware and Chesapeake Bay area of Baltimore, Maryland. Transactions of the American Microscopical Society 85: 115-130.

Kützing, F.T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.

Levkov, Z. (2009). Amphora sensu lato. In Diatoms of Europe, Volume 5. (H. Lange-Bertalot, ed). A.R.G. Gantner Verlag K.G. 916pp.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Amphora bicapitata CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

This taxon was first found and described in the estuarine Middle River just outside Baltimore, Maryland (Hohn and Hellerman 1966). In 2014, a USGS stream survey in the southeast US collected it at several more localities, varying in distance from 70-200 km from the East Coast, in Virginia, North Carolina and South Carolina.