Habitat:  Australian Sea, probably Bass Strait. (It also occurs in Algoa Bay.)

20.  DIACHORIS, n. gen.  Table 1 figures 10 to 12.

Cells separate, each connected with six others by short tubes; disposed in a horizontal plane, and forming a continuous irregular frond; free, or partially adnate.

The mode of arrangement and interconnection of the cells in this genus is remarkable, and highly interesting.  It represents, in fact, a dissected Flustra or Membranipora.  The cells are disposed in linear parallel series, and those of two contiguous series are alternate with respect to each other.  Each cell is connected with one at either end in the same linear series by a rather wide short tubular prolongation, and with two on each side in the contiguous series by narrower tubes, so that each cell, except in the marginal rows, is connected with six others.  It is this mode of interconnection of the cells that affords the diagnostic generic character.  There is but one species in the present collection, but in Mr. Darwin’s there are two others from the Straits of Magellan, as yet undescribed.

1.  D. crotali, n. sp.  Table 1 figures 10 to 12.

Cells erect, open in front, perforated on the sides and bottom; a lanceolate appendage articulated to each upper angle.  Ovicell conical, placed on the upper edge.

Habitat:  Bass Strait, 45 fathoms.

The frond, though not strictly speaking adnate, as it seems to have no attachments, is usually spread loosely over other polyzoa.  There is no appearance of a movable mandible in the lanceolate appendages, but which, nevertheless, most probably represent avicularia.  These organs are of a lanceolate form, with an elevated ridge or keel along the back, and slightly concave beneath.  They project in front, slightly depending; and at the base of each is a rounded eminence.

Fam. 6.  CELLEPORIDAE.

Polyzoarium missive or crustaceous, composed of ovate cells in juxtaposition and arranged, more or less regularly, in linear series, radiating from a central point or line.

21.  CELLEPORA, Otho Fabricius.

1.  Cellepora bilabiata, n. sp. ?

C. labiata, Lamouroux.

Cells deeply immersed; mouths in some entire and unarmed; in others, with two acuminated conical lips; immediately beneath the apex of the posterior lip a small sessile avicularium.  Ovicells subglobular, with a scutiform area on the upper surface, marked with several lines on each side, radiating from a central line.

Habitat:  Bass Strait.

Parasitic on several zoophytes.  This species to the naked eye exactly resembles C. pumicosa, but on closer examination several important differences will be observable.  The cells in C. bilabiata are less rounded and less distinct than in C. pumicosa.  As in that species, some of the cells are furnished with an avicularium, and others unprovided with that appendage; and again, some cells support an ovicell,