1.  F. pyriformis ?, Lamouroux.

Cells pyriform, or barrel-shaped, prominent, marked with transverse wrinkles.  Ovicells lofty, keeled in front, with a strong central, and two lateral longitudinal ribs.

Habitat:  Bass Strait, 45 fathoms.

Sometimes small and parasitic, upon Sertularians and Polyzoa—­sometimes independent, then of large growth, forming dichotomously divided fronds, with strap-shaped truncate, unequal divisions.

b.  Cells on both sides. (Carbasea, Gray.)

2.  F. denticulata, n. sp.

Cells much elongated, narrow; sides parallel, ends square; an upturned spine on each side at the oral end; sides of cell denticulate, denticles very numerous, small, acute.  Avicularia irregularly distributed on the surface of the frond.

Habitat:  Bass Strait, 45 fathoms.

Frond divided into numerous strap-shaped, truncated segments, of various widths; it attains a height of several inches.  In habit it is very like some forms of F. truncata, and there is a Mediterranean species (undescribed ?) in which the cells are denticulate, much in the same way as in the present species, but otherwise quite distinct.

18.  RETEPORA, Lamarck.

Character. (B.) Polyzoarium foliaceous, calcareous, or horny, reticulate; cells only on one side.

1.  R. cornea, n. sp.

R. ambigua ?  Lamarck.

Cells oval, not very regularly arranged, in a continuous, foliaceous, subcircular frond; reticulated with oval spaces, not as wide as the interspaces.  Ovicells large, galeriform, immersed, smooth.

Habitat.  Off Cumberland Islands, 27 fathoms, fine grey mud.

This remarkable species is so completely a Retepore in construction, that it seems impossible to separate it from that genus, merely from the circumstance that its composition is more horny than calcareous.  The frond is more or less orbicular, or rather is composed of more or less orbicular or reniform folds, one over another, and attached as it were to a common centre.  The substance is very thin and transparent, and the interspaces are much broader than the elliptical spaces.

2.  R. cellulosa.

Habitat:  Bass Strait, 45 fathoms.

Not distinguishable from a Mediterranean specimen.

3.  R. ctenostoma, n. sp.

Frond umbilicate, irregularly infundibuliform, spaces elongated, narrow, margins subdenticulate; interspaces as wide as the spaces.  Mouth of cells tubular, projecting; with six or seven unequal acute expanding teeth.

Habitat:  Bass Strait, 45 fathoms.

A very distinct and beautiful species.  The frond is about half an inch wide, and though really umbilicate and subinfundibuliform, does not at first sight appear so, being much more expanded on one side of the centre than on the other.

19.  ESCHARA, Ray.

1.  E. lichenoides, M. Edwards.  Mem. sur les Eschares.  Ann. d.  S. N. tome 6 page 31 plate 2 figure 3.