ved that four will be
found to be new, or hitherto undescribed, and it has been deemed
requisite to modify the characters of several others upon the more
extended survey of species afforded mainly by the present collection. The
new genera here instituted are:

Calpidium.
Diachoris.
Didymia.
Dimetopia.

And the genera whose characters it has been found requisite to modify
are:

Catenicella.
Salicornaria.
Cellularia.
Scrupocellaria.
Bicellaria.
Canda.
Emma.
Acamarchis.
Caberea.

Of the twenty-four genera, three, or perhaps four, appear to be peculiar
to the Australian seas. These are:

Calpidium.
Canda ?
Didymia.
Dimetopia.

All the rest, excepting two, Emma and Diachoris, appear to be distributed
over the globe in both hemispheres. The above two are perhaps limited to
the southern.

Of the fifty-three species, about thirty-three seem to be new, or to have
been so imperfectly described as not to admit of precise identification,
and five others have synonyms more or less doubtful applied to them.

Six species only are common to the seas of Europe, namely:

Tubulipora phalangea ?
Crisia denticulata.
Eucratea chelata.
Anguinaria spatulata.
Acamarchis neritina.
Retepora cellulosa.

Sixteen others are met with in other parts of the Southern hemisphere,
namely:

Catenicella elegans ?
Catenicella ventricosa.
Eschara lichenoides, occurring in Algoa Bay.
Caberea zelanica.
Acamarchis tridentata, in Algoa Bay and New Zealand.
Caberea lata.
Catenicella hastata.
Catenicella cribraria.
Catenicella cornuta.
Cellularia monotrypa.
Bicellaria tuba, in New Zealand and
Emma crystallina.
Emma tricellata, in New Zealand and Campbell's Island.

Thus of the fifty-four species, about thirty-four would seem to be
peculiar to the Australian seas. Ten of these belong to the genus
Catenicella, and one to the closely-allied Calpidium, three to Didymia
and Dimetopia, and one to Diachoris, of which genus two other species are
found in the Straits of Magellan.

The method according to which the Polyzoa are arranged, is, in the
primary divisions at least, pretty nearly identical with that indicated
in the Synopsis of the Families and Genera of Polyzoa Infundibulata,
given in Dr. Johnston's British Zoophytes.*

(*Footnote. Volume 1 page 263 2nd Edition.)

A few words, however, will be necessary to explain more particularly the
subsequent subdivisions here adopted.

The order, Polyzoa infundibulata, is divided in