1921.] A. Robertson: Ri'porl on Bryozoa. 49 



seems to consist of a slit or opening under the operculum. Above 

 and close to the calcareous margin is a rather broad, delicate, 

 semi-chitinous rim (chi. r.) against which the spiny operculum 

 closes. The space formed by the opening of the operculum consti- 

 tutes a secondary mouth. Moreover the heavy operculum fre- 

 quently tears away from the delicate membrane of the area, 

 leaving an opening between operculum and area having the 

 appearance of a mouth. This was confusing until, after soaking 

 small pieces in oil for a few hours, then teasing on a slide, 

 instances weie found in which the operculum was thrown back 

 and opened as in fig. 5, B. It is im])ortant that this species be 

 examined further, either fresh or preserved in alcohol. 



Brackish Water Membranipora. 



The three species of Membranipora which follow belong to 

 brackish-water forms similar to Membranipora bcngalensis des- 

 cribed bv Stoliczka (1869). That investigator found this species 

 in a tank of water only one-fifth as saline as sea-water. Later he 

 found it distributed throughout that region of India known as the 

 Sunderbans, incrusting old pieces of wood, or trunks of trees at the 

 mouths of rivers and on the shores of salt lakes, but never in fresh 

 water. In his description of this species, Stoliczka remarks that 

 he has observed similar forms incrusting shells and fragments of 

 wood in various places along the coast of Bengal Bay, but had not 

 succeeded in obtaining specimens which were in a good state of 

 preservation. 



In this collection there are three species of Membranipora 

 which have proved most puzzling until the description and plates 

 of M. bengalensis were obtained. These three species resemble 

 each other and M. bengalensis in several features: (i) in the loose 

 connection existing between the zoaria and the substratum, and 

 often between the zocecia themselves ; (2) in the possession of 

 delicate chitinous rather than calcareous lateral walls, together 

 with an extremely delicate calcareous wall over portions of the 

 front of the zocecia; (3) in the development, as a rule, of con- 

 spicuous spines which are highly characteristic and distinct for 

 each species. Like M . bengalensis also, all grow on wood more or 

 less sodden or on shells of brackish- water mollusks. 



31. Membranipora amoyensis, sp. nov. 



Zoarium loosely incrusting a shell and in places forming 

 bilaminar folds. ZocBcia large, quadrasgular, alternate, separated 

 by thickened lines (fig. 6). Aperture occupying more than half 

 the front. Operculum semicircular, large, situated close to the 

 top. Aperture surrounded by a calcareous margin from which 

 project numerous small calcareous spines, 17 or 18, or perhaps 10 

 to 12, depending on the size of the zooecium. On young zooecia a 

 single stout spine on each side at the upper angles. On older 



