Notes on Iowa Diatoms III. Occurrence of the Genus Pleurosigma in the Des Moines River

A member of the diatom genus Pleurosigma was collected from the Des Moines River from 12 stations. Earlier investigators did not report it. This organism may be suitable as an ecological indicator, since most members of the genus occur in salt or brackish water. Positive identification was not made, the organism is probably a variety of P. delicatulum Wm. Smith