118 Descriptions of New, 



M. mamillaris, armata, dispar, and Woodsii differ from 

 the other species in having the operculum distinctly hinged, 

 and form a well defined subgeneric or, rather, generic group, 

 for which I would propose the name Thairopora, the 

 definition being — Cells separated by raised margins ; front 

 entirely membranous or membrano-calcareous ; operculum 

 articulated by a distinct hinge. 



Membranipora permwnita, Hincks. 



This species is the same as I described in 1869 as M. 

 fcdcata ; but as my description was taken from a bad speci- 

 men, in which the peculiar marking of the ovicell was 

 obliterated by calcareous overgrowth, and was accompanied 

 by no figure, I think it preferable to adopt Mr. Hincks' 

 name. Sometimes the rim on the ovicell is scarcely, or not 

 at all, perceptible, and the ovicell projects much more than 

 usual. It may always be distinguished by the peculiar 

 structure of the falciform avicularium, one side of the 

 mandible of which is thickened and the other expanded into 

 a thin, membranous wing. In some specimens there are one 

 or two blunt, rounded elevations at the base of the cells. 



Membranipora polita, Hincks, Fig. 8. 



Mr. Hincks has recently described the present species from 

 specimens obtained at Glenelg. I have little doubt that it 

 is identical with Lamouroux's Cellepora alata. The cells are 

 very porcellanous, close together, distinct, narrowed down- 

 wards. The aperture occupies about one-third or more of 

 the cell. Below, the cell is elevated into a rounded or oval 

 protuberance, and on each side of the aperture is thickened 

 into an oval or elliptical mass. These convexities are not 

 always distinctly marked ; occasionally there is a thick collar 

 all round the aperture, and sometimes there are several trans- 

 verse marks across the front of the cell. At the growing 

 extremity of one specimen the cells spread irregularly, in the 

 manner of Membranipora catenularia, to which it is nearly 

 related. The latter species is usually described as an 

 Hippothoa, from the true species of which it differs entirely 

 in the structure of the cell; and I quite agree with Hincks in 

 referring it to the Membraniporidae, of which it ought 

 probably to form the type of another genus, including the 

 present species and Hippothoa crassa. 



I have found it at Queenscliff, encircling the stems of 

 Cymodocea antarctica. 



