Semiorbis catillifera

(Morrow) G.Reid and D.M.Williams 2010      Category: Eunotioid
BASIONYM: Eunotia catillifera Morrow 1981

Sellaphora wallacei


Semiorbis rotundus

LM scalebar = 10 µm = 80 pixels.


Contributor: David R.L. Burge | Mark Edlund - July 2016
Length Range: 17-40 µm
Width Range: 4.8-5.3 µm
Striae in 10 µm: 12-13


Valves are weakly arcuate. The dorsal margin is more strongly curved than the ventral margin. In larger specimens, a weakly gibbous shoulder can be observed on the dorsal margins near the apices. Apices are subcapitate, slightly recurved dorsally and narrow (2.0-2.5 µm) . Striae are nearly parallel and are interrupted by a hyaline line near the ventral margin. The striae are separated by externally thickened, transapical costae. The costae terminate on the dorsal margin as prominent, planar wing- or spine-like projections. A reduced raphe is present on the ventral mantle interface at the apices, but it can be difficult to discern in LM. Areolae are not resolvable in LM. Rimoportulae are absent.

Original Description

Basionym: Eunotia catillifera
Author: Morrow 1981
Length Range: 10-42 µm
Width Range: 2.8-6.1 µm
Striae in 10 µm: 11-14

Original Description

Frustule in ventral girdle view rectangular, in dorsal view sometimes broader in middle than on ends. Dorsal valve margin strongly convex, ventral margin slightly concave. Ends of valve rostrate-capitate. Terminal nodules above ventral margin near valve apices. Striae parallel, alternating with plates which obscure them. Plates fin-like, diminishing in size toward valve ends. Raphe partly on ventral valve mantle and partly on valve face. Striae 11-14 in 10 µm. Length 10-42 µm. Breadth 2.8-6.1 µm.

Original Images

Cite This Page:
Burge, D., and Edlund, M. (2016). Semiorbis catillifera. In Diatoms of the United States. Retrieved April 21, 2018, from

Species: Semiorbis catillifera

Contributor: David R.L. Burge | Mark Edlund

Reviewer: Jen Beals


Morrow, A.C., Deason, T.R. and Clayton, D. (1981). A new species of the diatom genus Eunotia. Journal of Phycology 17: 265-270.

Reid, G. and Williams, D.M. (2010). Notes on the genus Semiorbis Patrick with a description of a new species. Diatom Research 25: 355-365.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA
Original INA

California Academy of Sciences (CAS)

Semiorbis catillifera CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Semiorbis catillifera was described from epiphytic and epipsammic habitats in a shallow, slightly acidic stream in western Florida (Morrow et al. 1981). The images shown here are of the holotype slide.