a General History of the Marine Polyzoa. 7 
In the present form the membranous wall appears to be of 
stouter material, and the margins of the cells are more 
distinct; the zoarium is always of a brownish colour. <A figure 
of M. hexagona is given for comparison with the present 
form (Pl. IV. fig. 6). 
Family Microporide. 
Microprora, Gray. 
Micropora coriacea, Ksper, var. 
The variety without the marginal knobs, which Ihave figured 
In a previous paper (‘ Annals,’ November 1880, pl. xvi. 
fig. 6), occurs amongst Capt. Warren’s dredgings. The 
avicularia, which are sparingly developed on British speci- 
pets of this species, are very abundant on those from Aus- 
tralia. 
STEGANOPORELLA, Smitt. 
Steganoporella magnilabris, Busk. 
This species, which is commonly found incrusting, forms in 
Bass’s Straits erect, bilaminate, foliaceous expansions of con- 
siderable size; it was obtaimed by Pourtales in a similar 
condition off the coast of Florida. It seems to be very vari- 
able in its mode of growth, and might pass in turn for a 
Lepralia, Eschara, and Siphoneila, under the older systems. 
Family Cribrilinide. 
CRIBRILINA, Gray. 
Cribrilina ferox, MacGillivray. 
I have some doubt whether this curious species should be 
referred to the genus Cribrilina. ‘The structure of the cell- 
wall seems to be peculiar, and may possibly afford a basis for 
a new generic group; but my specimens do not yield the 
material for a satisfactory study of the development of the 
zocecium. 
It is a point of much interest (not noted in MacGillivray’s 
description) that this species exhibits the remarkable peculi- 
arities which I have described as occurring in Membranipora 
radicifera. 
The cells are connected as in the latter form; and the 
zoarium is attached by means of radical tubes originating 
from the dorsal surface. The specimens which occur are 
growing upon sponge, the soft substance of which is pene- 
