In the Celleporidæ, (Case B 1) the cells are typically pitcher-shaped and arranged vertically, and tend to be heaped up from the overcrowding.
Cellepora pumicosa forms thick pumice-like masses composed of succeeding layers of cells. The Reteporidæ (Case B 1) form delicate stony networks. The reticulate fronds may be expanded out, or may form tubular or contorted growths (Fig. 15, Retepora beaniana). The beautiful Retepora phœnicea from Torres Straits is of a rich purple colour.
The Adeonidæ form thick fenestrated plates which unite to form cavernous masses usually attached to rocks by a thick jointed stem. Several very fine examples from Port Phillip, Victoria, are exhibited in the upright part of Case B.
Case A 2.
The Catenicellidæ are represented by a fine series of specimens from Australia. The colonies form dense clusters of finely beaded branches. The cells are arranged in single series, each cell being united to those above and below by a horny joint. The cells are usually urn-shaped with a triangular avicularium at each upper angle, and with the front surface variously sculptured with pores or bands (Fig. 16, Catenicella ventricosa).
Fig. 16.
Catenicella ventricosa. A, natural size; B, magnified. (After Busk.)
Sub-order 2.—Ctenostomata.
Case B 2, and A upright part.
The Ctenostomata are fleshy, horny, or membranous; never calcareous. When the tentacles of a polypide are retracted into the cell, they are protected above by a membranous comb-like frill.