With the exception of _Victorella_, which occurs more commonly in brackish than in fresh water and has been found in the sea, the genera that occur in fresh water are confined or practically confined to that medium; but certain marine ctenostomes and cheilostomes not uncommonly make their way, both in Europe and in India, into brackish water, and in the delta of the Ganges an entoproctous genus also does so. The ctenostomatous genera that are found occasionally in brackish water belong to two divisions of the suborder, the Vesicularina and the Alcyonellea. To the former division belongs _Bowerbankia_, a form of which (_B. caudata_ subsp. _bengalensis_, p. 187) is often found in the Ganges delta with _Victorella bengalensis_. No species of Alcyonellea has, however, as yet been found in Indian brackish waters. The two Indian cheilostomes of brackish water belong to a genus (_Membranipora_) also found in similar situations in Europe. One of them (_M. lacroixii_[AZ]) is, indeed, identical with a European form that occurs in England both in the sea and in ditches of brackish water. I have found it in the Cochin backwaters, in ponds of brackish water at the south end of the Chilka Lake (Ganjam, Madras), on the shore at Puri in Orissa, and in the Mutlah River at Port Canning. The second species (_M. bengalensis_, Stoliczka) is peculiar to the delta of the Ganges[BA] and has not as yet been found in the open sea. The two species are easily recognized from one another, for whereas the lip of _M. bengalensis_ (fig. 33) bears a pair of long forked spines, there are no such structures on that of _M. lacroixii_, the dorsal surface of which is remarkably transparent. _M. lacroixii_ forms a flat zoarium, the only part visible to the naked eye being often the beaded margin of the zooecia, which appears as a delicate reticulation on bricks, logs of wood, the stems of rushes and of hydroids, etc.; but the zoarium of _M. bengalensis_ is as a rule distinctly foliaceous and has a peculiar silvery lustre. [Footnote AZ: There is some doubt as to the proper name of this species, which may not be the one originally described as _Membranipora lacroixii_ by Andouin. I follow Busk and Hincks in my identification (see Cat. Polyzoa Brit. Mus. ii, p. 60, and Hist. Brit. Polyzoa, p. 129). Levinsen calls it _M. hippopus_, sp. nov. (see Morphological and Systematic Studies on the Cheilostomatous Bryozoa, p. 144; Copenhagen, 1909).] [Footnote BA: Miss Thornely (Rec. Ind. Mus. i, p. 186, 1907) records it from Mergui, but this is an error due to an almost illegible label. The specimens she examined were the types of the species from Port Canning. Since this was written I have obtained specimens from Bombay--_April_, 1911.] [Illustration: Fig. 33.--Outline of four zooecia of _Membranipora bengalensis_, Stoliczka (from type specimen, after Thornely). In the left upper zooecium the lip is shown open.]