Two distinct species appear to have been confused by James-Clark in his original description of Bicoeca lacustris. The two forms have been re-examined and photographed. It is suggested that the differences between them justify their separation into two species, as suggested by Stolc, the one form to retain the name B. lacustris, the other to receive that of B. vacillans Stolc. A new species. B. maris, is described, and the affinities of the Bicoecidae, Bodonidae and Craspedomonadidae are discussed.