A large number of samples of Salpidae, Doliolidae and Pyrosomatidae, collected by the U. S. Ocean Acre Project, are studied. A new record for the Bermuda area of Doliopsis rubescens (Vogt, 1817) is given. Dominant species are Iasis zonaria (Pallas, 1766), Salpa fusiformis Cuvier, 1804, and Salpa aspera Chamisso, 1819. Seasonal peak occurrences are observed for several species. The seasonal and vertical variation of the number of muscle fibres of aggregate Salpa fusiformis and aggregate Salpa aspera is studied and discussed.