Fenestrate bryozoans in Chesterian rocks of the eastern United States are common to abundant in diverse carbonate platform lithologies but are not common in clastic deposits. Fenestella and Archimedes are the most abundant and widespread. Fenestella apparently tolerated a range of water agitation and lived on shoal margins as well as in more protected areas. Archimedes required quiet bottoms and was locally extremely abundant immediately leeward of shoals. Polypora and Septopora were less common than, but had a similar distribution to, Fenestella except that they apparently did not live on shoals. Lyroporella inhabited zones of pronounced current activity and fine quartz sand influx. Penniretepora and Ptylopora were least often encountered, restricted to fine-grained sediments deposited in protected regions.