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THE VOYAGE OE H.M.S. CHALLENGER. 
3. Steganoporella, Smitt. 
Steginoporella, Smitt, Florid. Bryoz. 
Steganoporella ; Hincks, Brit. Mar. Polyz. ; Waters ; Macgilliv. 
Membranipora (pars), Brit. Mus. Cat.; Auctt. 
Vincularia (sp.), d’Orb. 
Character . — Zoarium polymorphous; erect and branched or lobate; or decumbent, and 
foliaceous and crustaceous. Zooecia oblong, arched above. Frontal area occupied by a 
delicate chitinous membrane, which is closely adnate to the internal calcareous lamina 
for about the lower half of the area ; above free, and supporting the operculum, and 
having on each side, below the orifice, a minute forked or irregularly branched vertical 
chitinous rod. Opercula large, semicircular, usually of two kinds, the membranous 
portion supported by a branching chitinous framework. A strong internal calcareous 
lamina, which, about the middle of the length of the cell, bends backwards to the 
posterior wall, forming a transverse diaphragm, by which the cell is divided into two 
distinct chambers, communicating by a phrenic opening through which the polypide 
is protruded supported on or passing over a large hollow process rising from the upper 
and anterior part of the transverse diaphragm. 
The very peculiar conformation of the zocecium in this genus or subgenus is not very 
easily described. It may be briefly said that the general cavity of the zooecial cell is 
divided into two chambers, an upper, probably ooecial in function, in the fertile cells, and 
an inferior, in which the polypide is lodged. This division into two chambers is effected 
by the bending backwards of the calcareous lamina, which, instead of ceasing with a free 
border as in Vincularia ( mihi ), is apparently attached all round to the sides and back of 
the general zooecial cavity, but leaving posteriorly a rather large opening, through which 
the polypide is extruded along an imperfectly tubular passage which bends forwards to the 
orifice, and is supported beneath by a very peculiar hollow process rising from the convex 
upper surface of the diaphragm. 
The space, therefore, of the upper chamber, on each side of the diaphragmatic 
opening and supporting fulcrum, forms a vaulted cavity occupying the upper half of the 
entire cell, and no doubt, as has been suggested, serving as an ooecial receptacle. There 
are no other distinctly ooecial organs. In two out of the three existing species of the 
genus, limited as above, with which I am myself acquainted, this upper or ooecial compart- 
ment is more developed in some of the zooecia than in others, and the difference is marked 
1 
by a difference in the size and pattern of the chitinous framework of the operculum. In the 
third species, a New Zealand form, which I have termed Steganoporella neo-zelanica? 
which docs not occur in the Challenger collection, there is, however, no marked difference 
between the opercula of different cells. Other peculiarities, not at first sight so obvious 
1 Quart. Journ. Micr. Sci., N. S., vol. i. p. 155, pi. xxxiv. fig. 4. 
