a General History of the Marine Polyzoa. 85 



which adds to the picturesqueness without at all impairing 

 the beauty of the species. 



The zooecia are turned over, as it were, towards the inner 

 side ; and on this side, of course, no cell-wall is to be seen, 

 the margin of the aperture lying close against the neighbour- 

 ing cell, whilst on the opposite a considerable tract of it is 

 visible. In most of the branches a central line of zocecia is 

 traceable, which are straight and of the usual appearance ; 

 and on each side of this line the zocecia turn inwards towards 

 it, so that those on the opposite sides face one another. 



The wall below the aperture is prettily ornamented with 

 minute punctures. The sinuated appearance of the margin 

 of the aperture is caused by the spines, which exhibit a curious 

 peculiarity : the lower portion is solid ; but the points are 

 simply membranous, and in the dried state have either 

 shrivelled up or disappeared. 



There is an evident affinity between this interesting form 

 and the common M. jnlosa, Linn. 



b. With a calcareous lamina. 

 Membrantpora nitens, n. sp. (PI. XI. fig. 4.) 



Zoozcia quincuncial, somewhat pyriform, expanded above 

 and narrowed downward, prolonged below the aperture, closely 

 united to one another ; walls smooth and glassy ; aperture 

 ovate, occupying rather more than half the front of the cell, 

 with a thin smooth margin, covered in by a very transparent 

 membrane, which lies on a level with the edge, a very shal- 

 low calcareous expansion at the very base of the aperture ; 

 on each side, immediately below the upper margin, a small 

 white tubercle ; the portion of the cell below the aperture 

 bearing a single large boss or nodule, white and polished. 

 Avicularia none. Omcium (?). Zoarium lobed or branched. 



Loc. Australia, on a Polyzoon {Miss Jelly). 



This Australian form is certainly distinct from the South- 

 Atlantic M. tuberculata, Bosc (which is so commonly found on 

 the Gulf- weed), though it may be said to belong to the same 

 section of the genus. The general appearance of the zoarium 

 is bright and glossy, and is due in part to the polish of the 

 calcareous portions, and in part to the shining surface of the 

 membrane which closes the cells. The latter lies quite on a 

 level with the top of the margin, and extends to the very bottom 

 of the aperture, covering the slight calcareous plate. The two 

 small white tubercles immediately below the upper margin 

 are constantly present. There is a considerable prolongation of 

 the cell below the aperture j and this portion is almost entirely 



