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Diatoms of the United States is now known as Diatoms of North America.
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(Meneghini) San Leon 1848      Category: Centric
TYPE SPECIES: Melosira (Pleurosira) thermalis (Meneghini) San Leon




Image Credit: Pat Kociolek

CLASS: Coscinodiscophyceae
  ORDER: Triceratiales
    FAMILY: Triceratiaceae

  1. Valves orbicular
  2. Ocelli 2-4, prominent
  3. Rimoportula single, positioned near center of valve
  4. Valves form zig-zag colonies

Pleurosira has very large orbicular valves with 2-4 prominent ocelli, the number depending on salinity. The ocelli secret mucopolysaccaride pads that join cells together in large, zig-zag colonies. A single rimoportula is positioned near the center of the valve face. Colonies form filaments that are visible in streams.

Pleurosira is widely distributed in naturally saline waters and polluted waters. In older literature it was reported as a Biddulphia or Cerataulus.

Cite This Page:
Spaulding, S., and Edlund, M. (2008). Pleurosira. In Diatoms of the United States. Retrieved May 27, 2018, from

Contributor: Sarah Spaulding | Mark Edlund - December 2008
Reviewer: Sam Rushforth - June 2010