Specimens of freshwater bryozoans (Ectoprocta) and sponges (Porifera: Spongillidae), two of the most poorly known faunal groups in Canada, were obtained from various locations in Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland. A total of 14 species of bryozoans and 15 species of sponges were identified. In 31 cases, these species were recorded from a province for the first time. Species new to Canada include the bryozoans Lophopodella carteri, Plumatella orbisperma, and Pottsiella erecta, and the sponges Radiospongilla crateriformis, Spongilla aspinosa, and Trochospongilla horrida. The morphology, taxonomy, distribution, and ecology of each species are examined. Several taxonomic revisions are made. Eunapius mackayi and Plumatella orbisperma are redescribed. Spongilla heterosclerifera, considered an endangered species, is shown to be a species mixture. Taxonomic keys to Eastern Canadian species of freshwater bryozoans and sponges are presented. New limits of tolerance to pH, calcium and magnesium levels, and water temperature are established for several species.

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