t is a
Bicellaria: it differs from all other species of that genus, however, in
the absence of any long spines, and in general habit. Were it not
referred to that genus, it would probably constitute the type of a
distinct one. A curious little trident-like organ is visible in the
narrow part of some cells.

15. ACAMARCHIS, Lamouroux.

Character. (B.) Cells elliptical,* closely contiguous; opening very
large, margin simple, not thickened. Avicularia not always present, like
birds' heads.

(*Footnote. Viewed posteriorly.)

To which may be added, that the species are frequently coloured, red or
bluish.

1. A. neritina, Lamouroux.

Habitat: Rio de Janeiro. Broken Bay, New South Wales.

This species appears to be one of the most generally distributed of the
Polyzoa; it occurs in nearly every latitude in both hemispheres.

2. A. tridentata. Krauss. Corall. d. Sudsee page 3 figure 2.

Habitat: Bass Strait (?)

This species is placed doubtfully in the Rattlesnake Collection. It
occurs, however, in Van Diemen's Land and New Zealand (Dr. Hooker) and is
abundant in South Africa.

Fam. 4. CABEREADAE.

Polyzoarium entirely divided into ligulate dichotomous bi or multiserial
branches; back nearly covered by large vibracula; avicularia sessile.

16. CABEREA, Lamouroux.

Selbia, Gray. op.c. Volume 2 page 292.

Cells bi-multiserial, in the latter case quincuncial. Posterior surface
of branches concealed by large vibracula, which are placed obliquely in a
double row, diverging in an upward direction from the middle line, where
the vibracula of either row decussate with those of the other. Avicularia
when present of the flexible kind, sessile on the front of the cell.

The remarkable feature of this genus resides in the vibracula, which here
appear to attain their utmost development. Each vibraculum appears to
belong not to a single cell as in Scrupocellaria, but to be common to, or
applied to the backs of several. They are more or less pyriform or long
oval in shape, and the two rows decussate with each other along the
middle of the branch--giving in the narrower species, especially, much
the aspect of an ear of barley, and in the wider of a straw plait. The
walls of the vibracula are usually thin, and very transparent, so as to
allow the outlines of the cells to be seen imperfectly through them. The
upper and outer extremity of the vibraculum is bifid, and to the inner
horn is articulated the seta, and from the notc