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

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

Habitat: Ba.s.s 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 notch between the two horns there is continued nearly, if not quite, to the inner extremity of the organ, and along its upper border, a shallow groove, in which is lodged the seta when in a state of rest. In most species the seta is serrated with distant teeth on one side.

Where there are more than two rows of cells, the marginal cells differ in conformation from the central.

As in Scrupocellaria, the opening of the cell is sometimes protected by a pedunculate operculum. The genus, therefore, may, like that, admit of being divided into sections, distinguished respectively by the presence or absence of a pedunculate operculum.

a. Operculatae.

1. C. rudis, n. sp.

Multiserial; opening of cells oval, margin much thickened, with a strong projecting upturned spine on each side in the central cells, and with three strong and long similar spines on the outer side, and a smaller one on the inner side in the marginal cells. Operculum spatulate, or pointed above, entire. Each cell of the central rows with two small avicularia in front, immediately below the mouth. Each marginal cell with a single large vibraculum in front below the mouth. Vibracula slender, very transparent. Setae short, not serrated.

Habitat: Ba.s.s Strait.

Colour dirty white: forms a broad frondose polyzoarium 1 1/2 to 2 inches, or perhaps more, in height. The branches, all disposed in the same plane, are flat, thick, and about 1/8th of an inch wide, composed of from four to six rows of comparatively small cells, which viewed behind appear lozenge or diamond-shaped, and arranged quincunically. It is not always easy to observe with accuracy the outline of the vibracula, owing to the extreme tenuity of their walls, but the groove along the upper border is very distinct and most usually has the seta lying in it. The avicularia on the marginal cells are very large, but not uniform in size. Along each border of the branches runs a bundle of radical tubes, the number of which diminishes as the branch ascends, each terminating in a vibraculum.

2. C. zelanica, Busk.

Selbia zelanica, Gray. Dieffenbach's New Zealand, volume 2 page 292.

Crisia boryi, Audouin. (Savigny Egypt plate 12 figure 4.)

Biserial; opening of cell oval or elliptical, rounded at each end, crossed in front, and thus divided into two nearly equal parts by a transverse calcareous band, from the lower edge of which depends a pedunculate, falciform operculum. Cells frequently produced upwards into a large arcuate ovicell. Vibracula ovoid, setae long, serrated.

Habitat: off c.u.mberland Islands, 27 fathoms, fine grey mud.

Slender: sufficiently distinguished by the peculiar form of the operculum. This part is so indistinctly represented in Savigny's figures, as to render it impossible to determine with certainty whether his species is the present one or not. The posterior view is much more like, but that is insufficient of itself to afford a specific character. The back of the branches exactly resembles an ear of barley. This species occurs in New Zealand, and also in South Africa.

b. Inoperculatae; opening of cell without an operculum.

3. C. lata, n. sp. ?

C. dichotoma ?, Lamouroux.

Branches 4 to 7 serial; opening of cells in central rows, oval, sometimes square below; and the cell frequently produced into a shallow arcuate cavity. A short blunt spine on each side of the mouth. Marginal cells shallow, opening oval, margin much thickened, granulated: usually a short conical spine at the summit; a very minute sessile avicularium behind the outer edge, superiorly. Vibracula very large: setae serrated.

Habitat: off c.u.mberland Islands, 27 fathoms fine grey mud.

Colour white or yellowish; forms close rounded tufts 2 1/2 to 3 inches in height and width, composed of uniform dichotomously divided branches, about 1/8 of an inch wide, and which become wider towards their truncate extremities. The vibracula are very large, and though distinctly defined, are yet sufficiently transparent to allow a view of the lozenge-shaped cells. The central rows of cells vary in number from two to five, and the cells composing them are arranged with extreme regularity. The marginal rows are placed in a plane posterior to the central, and as above noticed, the cells of which they are composed are widely different from the central.

The only other species with which the present can be confounded is Caberea hookeri (Cellularia hookeri, Fleming) a British form. The latter species appears to differ from C. lata, chiefly in its having a large tubular spine on each side of the mouth of the lateral cells, and in each of the central cells, or nearly so, being furnished with an anterior avicularium, below the opening and to one side. The lateral sessile avicularium on the marginal cells is also much larger.

Fam. 5. Fl.u.s.tRADAE.

Polyzoarium expanded, continuous or encrusting. Cells disposed in straight series, which do not radiate from a centre.

17. Fl.u.s.tra, Linn.

a. Cells on one side only.

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: Ba.s.s 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: Ba.s.s 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 h.o.r.n.y, 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 s.p.a.ces, not as wide as the inters.p.a.ces. Ovicells large, galeriform, immersed, smooth.

Habitat. Off c.u.mberland 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 circ.u.mstance that its composition is more h.o.r.n.y than calcareous. The frond is more or less...o...b..cular, or rather is composed of more or less...o...b..cular or reniform folds, one over another, and attached as it were to a common centre. The substance is very thin and transparent, and the inters.p.a.ces are much broader than the elliptical s.p.a.ces.