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Diatoms of the United States is now known as Diatoms of North America.
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The siliceous parts of the diatom cell wall. Composed of the larger epitheca and the smaller hypotheca. The epitheca overlaps the hypotheca similar to a pill box or Petri dish. From Latin for a little piece.

See also valve and cingulum.


Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.