Cellulariidae (for instance in Caberea Darwini, C. Boryi etc.) in 
whom the so-called fornix, a scutiform marginal spine which in a 
number of species. protects the membranous area, has reached its 
maximum. The proximal margin of the operculum is here limited 
by the distal margin of the fornix. In Coilostega it is found in 
Micropora, Monoporella, Chlidonia and Cellaria and besides in a 
number of Camarostega (Microporella, Tubucellaria, Onchopora 
Sinclairi, Chorizopora Brognarti etc.).… With the exception of 
Chorizopora Brognarti all those Camarostega which possess a simple 
operculum are also provided with a median pore no doubt serving 
as opening into the compensation sac. AÅ simple calcified opereulum 
is found in Membranipora monostachys, Monoporella erassatina 
and Micropora coriacaY), but while in the first named species the 
calcified operculum lacks a covering membrane, the calcified layer of 
the operculum in the two other species is invested with the same 
membranous epitheca as the front-wall of the zooecium. Consequently - 
we have to do here with a similar distinction between a calcified 
ectocyst and a cryptocyst as that which we have earlier spoken of. 
Also in the species of Cellaria”), in Micropora perforata and Mic. 
borealis I have found the operculum composed of two correspon- 
ding layers, an outer membranous and an inner chitinous. 
Rosette-plates and pores. After some times boiling in a so- 
lution of caustic potash most colonies of Bryozoa can be split in 
longitudinal rows of zooecia and the single zooecium conseqvently 
must have independent side-walls. On the contrary the proximal 
and the distal wall are common for every two contiguous zo0ecia. 
1) Under this name I think two different species have been confounded, 
but possessing only a very little rudiment of each I shall confine myself 
to point out some chief differences between the two forms. In. one 
of them (Hastings, Peal) the opereulum is calcareous, there is found 
an avicularium, and the ocecium is provided with a short, very narrow 
pore. In the other (Guernsey, Norman) the operculum is chitinous, 
medi is no avicularium and the lower part of the ocecium is sepa- 
from the superior minutely mugne part by an angular projection. 
2) Calvet. op cit. PI VI, fig. 11, op 
