Cellularudae (for instance in Caherea Darwini, C. Boryi etc.) in 
whom tlie so-called foniix, a scutiform marginal spiue which in a 
number of species protects the membranous area, has reached its 
maximum. The proximal margin of the operculnm is here limited 
by the distal margin of the fornix. In Coilostega it is found in 
Mici'opora, Monoporella, Chlidonia and Cellaria and besides in a 
number of Camarostega {Microporella, Tuhucellaria, 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. A simple calcified operculum 
is found in Memhranipora monostachys, Monoporella crassatina 
and Micropora coriaca ^). but while in the first named species the 
calcified operculum lacks a covering membrane, the calcified lajer 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 Mie. 
horealis I have found the operculum composed of two correspon- 
ding layers, an outer membranous and an inner chitinous. 
Rosette-plates and po7'es. 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 comraon for every two contiguous zooecia. 
0 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 
ol them (Hastings, Peal) the operculum is calcareous, there is found 
an avicularium, and the ooecium is provided with a short, very narrow 
pore. In the other (Guernsey, Norman) the operculum is chitinous, 
there is no avicularium and the lower part of the ooecium is sepa¬ 
rated from the superior minutely granular part by an angular projection. 
^) Calvet. op. cit. PI. VI, fig. 11, op. 
