6.  Calpidium, n. gen.  Table 1 figures 3 to 5.

Character:  Cells with an avicularium on each side; with two or three distinct mouths, arising one from the upper part of another, in a linear series, all facing the same way, and forming dichotomously-divided branches; cells at the bifurcation single; ovicells ——­ ?

This very peculiar genus, remarkable as it is, seems hitherto to have escaped notice.  It is distinguishable from Catenicella, in the first place, by the anomalous circumstance that each cell is furnished with two or more, usually three, distinct keyhole-shaped mouths, and is doubtless inhabited by three distinct individuals.  Whether these are separated from each other by internal partitions is unknown, but the closest examination of cells rendered transparent by means of acid fails to discover such.  In cells thus prepared, there are apparent, however, three distinct masses, reaching from the bottom of the cell to each orifice, and which are probably the remains either of the body or of the retractor muscles of the animals.  Another point of difference from Catenicella is the non-gemination of the cell at the dichotomy of a branch.  The avicularia, moreover, do not form lateral projections, but are sessile, or imbedded, as it were, in the sides of the cell immediately below the upper angles.

1.  C. ornatum, n. sp.  Table 1 figures 3 to 5.

Cells triangular-urn shaped, very broad above, with a straight border, much compressed; mouths, 2 to 3, keyhole-shaped.  Five fenestrae below each mouth; numerous branching bands on the back of the cell.

Habitat:  Bass Strait, 45 fathoms.

This curious species is the only one belonging to the genus.  The cells are very large, regular, and uniform, resembling very closely an antique sculptured urn.  Colour dark brown, and the walls so thick as to be nearly opaque.  The polyzoary, which appears to attain a height of four or five inches, is bipinnate (with all the branches on one plane) the branches alternate, and given off with extreme regularity.  The ultimate ramules are incurved.  The whole forms a very elegant object.  The central stem, or series of cells, differs in no respect as regards the size or disposition of the cells composing it, from the branches.

Fam. 2.  EUCRATIADAE.

7.  EUCRATEA, Lamouroux.

1.  Eucratea chelata, Lamouroux.

Habitat:  Bass Strait, 45 fathoms.

In all respects identical with the British form.  It also occurs at Port
Adelaide.

8.  ANGUINARIA, Lamarck.

1.  A. spatulata, Lamarck.

Aetea anguina, Lamouroux.

Habitat:  Bass Strait, and other localities.

This species (which appears to be pretty generally distributed over the globe) is identical with the European form.  It is to be remarked, however, that a second species (A. dilatata, Busk.  Annals of Natural History second series volume 7 page 81 plate 9 figure 14) is found in Torres Strait, but which does not occur in the Rattlesnake collection.