General History of the Marine Polyzoa. 369 
CO. fistulosa, it never, I believe, makes any approach to the 
size and stoutness of habit which we find in the present form. 
But the most important differences are found in the cell. The 
orifice is placed very low down, about the centre of it; the 
space above it is occupied by the opening to the ocecium, 
which is very large and circular in form. Round the upper 
part of the orifice there is a kind of border, which seems to 
pass downward behind it. 
The lower margin is elevated into a mucronate process, 
which more or less conceals a considerable portion of the 
opening, and in each corner, between it and the side walls of 
the orifice, is a conspicuous white denticle. The mucronate 
extension of the peristome is very conspicuous when the cell 
is viewed in profile. In C. fistulosa the lower margin is all 
but straight, and the denticles are (so far as my experience goes) 
wanting. The avicularium resembles in general character that 
of C. fistulosa, but it is very much wider and almost erect and 
has an extremely shallow mandible; the area on which it is 
placed is also of a different shape. 
In spirit-specimens a delicate membrane is present, which 
covers the whole of the front of the cell (including the ovarian 
opening), with the exception of the oral operculum. 
EXPLANATION OF THE PLATES. 
Prate XIII. 
Fig. 1. Membranipora marginella, 0. sp. 
Fig. 2, Membranipora favus, n. sp. 
Fig. 3. Microporella violacea, Johuston, form plagiopora, Busk, 
Fig. 4. Lepralia robusta, n. sp. 
Fig. 5. Porella malleolus, n. sp. 
Fig. 6. Smittia trispinosa, Johnston, form biémucronata, n. 
Figs. 7, 7 a. Smittia trispinosa, Johnston, var. 1. 
PLATE XIV. 
Fig. 1. Flustrella hispida, Fabr., form eylindrica,n. 1a, Nat. size. 
Figs. 2,2 a. Flustrella dichotoma, v. Suhr (sp.): zocecia, magnified. 2 6, 
Nat. size. 
Fig. 3. Pedicellinopsis fruticosa, n. gen. and sp.: group of polypides. 3a. 
Nat. size (about). 36, Two polypides. 3c. Portion of tube. 
Fig. 4. Cellaria fistulosa, var. australis, MacGillivray : zocecia, magnified. 
4a. A single cell, showing the origin of a branch. 46. Nat. 
size, Showing the peculiar mode of branching. 
