Some ecological observations on Urnatella gracilis Leidy

Specimens of U. gracilis were collected in benthic samples from the Trinity River, Texas in 1972. Physiochemical conditions of the river were determined at the time of collection. Chemical and physical data suggest that U. gracilis is tolerant to moderately polluted waters, but is never found in highly polluted waters. The presence of the phytoplankton gen Melosira may aid in explaining the distribution of umatella