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Monoraphid

Marginal lamina

 

Monotypic

Pennate diatoms having a raphe on only one valve. A monoraphid diatom is a type of heterovalvar diatom. Example genera include Cocconeis, Achnanthidium, and Eucocconeis.

During the ontogeny of monorahid diatoms, a raphe begins to form on each valve. One valve completes its raphe, and becomes the raphe valve. The other valve fills its incipient raphe with silica, leaving a thickened axial rib, and becomes the rapheless valve.

The genus Nupela includes some monoraphid species and some biraphid species. In this web flora, Nupela is included in the biraphid group.