Volume I Part 38 (2/2)

Cells opposite, in pairs.

22. DIDYMIA, n. gen. Table 1 figure 6.

Cells joined side by side; opening large, oval; mouth subapical, central.

No avicularium. Ovicells contained within a cell, which is central at each bifurcation.

1. Didymia simplex, n. sp. Table 1 figure 6.

Cells oblong, narrowed below, broad and truncate, with an angle externally above. Back marked with transverse rugae.

Habitat: Ba.s.s Strait, 45 fathoms.

A fine species, growing in loosely-branched phytoid fronds, to a height of several inches. In some (dried) specimens the branches are a little incurved, but not in all. The situation of the ovicell is peculiar. It is contained within the upper part of a cell placed between, or rather in front of the pair, from which the two branches at a bifurcation take their origin. The ovigerous cell differs widely in form from the others, being pyriform, and much attenuated below; and the orifice is below the middle. The upper compartment, in which the ovicell or sac itself is lodged, appears to be separated from the lower by a transverse diaphragm.

23. DIMETOPIA, n. gen. Table 1 figures 7 to 9.

Cells joined back to back; the mouths of each alternate pair looking in the same direction, and at rightangles to the intermediate pair.

1. D. spicata, n. sp. Table 1 figure 9.

Cells infundibuliform. Margin of opening much thickened, with six equidistant, elongated pointed spines.

Habitat: Ba.s.s Strait, 45 fathoms.

White, transparent, forming thick tufts about 1 1/2 to 2 inches in height. The same species also occurs in New Zealand.

2. D. cornuta, n. sp. Table 1 figures 7 and 8.

Cells suddenly contracted about the middle. Opening oval, wide above; margins slightly thickened with a short thick conical horn on each side above, and a long projecting spine (rarely two) in front below.

Habitat: Ba.s.s Strait, 45 fathoms.

Branches narrower than in the preceding species. Colour yellowish. Tufts loose; ovicell small in proportion to the size of the cells. It is placed immediately above and behind the upper margin of the opening of the cell to which it belongs.

Suborder 3. CTENOSTOMATA.

Fam. 1. VESICULARIADAE. Cells tubular, h.o.r.n.y.

24. AMATHIA, Lamouroux.

1. A. biseriata, Krauss. Corall. der Sudsee, page 23. Figure 1 a, b, c.

Habitat: Swan Island, Banks Strait.

The biserial arrangement of the cells is not a sufficient character, because in Amathia cornuta (Lamouroux) the cells are also biserial as well as in another South African species, very like the Australian form probably intended by Krauss, but apparently different from it. In the South African form the cells are shorter, narrower, and more cylindrical, and the branches are terminated by two lanceolate tags, which are not present in the Australian species, in which latter the cells also are wider, longer, and prismatic, or subhexagonal, with very thin walls.

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