Fam. 4. Pocilloporidae.—The general anatomy of the zooids of this family of corals has some resemblance to that of the Entocnemaria, and it is possible that they will eventually find a place in our classification near to, if not actually within that group. The fact, however, that the skeleton is imperforate is sufficient for the present to justify the inclusion of the family in the section Aporosa. There are but two genera at present known, and in both of them the zooids have twelve tentacles, twelve mesenteries, and only two mesenterial filaments. The zooids are connected together by an elaborate system of canals running in the superficial coenosarc. The calices are bilaterally symmetrical, and in Seriatopora the septa which are parallel with the axis of the branch are united in the centre of the calyx, and are very much larger than the others, as in Madrepora. In all these characters the family shows affinities with the Entocnemaria. In the characters of the skeleton, which is imperforate and tabulate, the affinities are rather with the Cyclocnemaria. The two genera are widely distributed on the coral reefs of the old world, and in some localities are very abundant. Neither genus is found in the West Indies. They are both of recent origin, but Pocillopora occurs in the Miocene. It is a remarkable feature of the family that both genera may be attacked by the gall-forming crab Hapalocarcinus. From some reefs nearly all the Pocilloporidae show crab-galls on a large number of their branches, whereas other Madreporaria are free from them.
Fig. 175.—A portion of a colony of Pocillopora from the Maldive Archipelago.
Fig. 176.—A single calyx of Pocillopora septata, showing Co, the columella; S, S, the septa; Th, the theca wall. (After Gardiner.)
Pocillopora is a coral that forms encrusting masses, rising into lobes or branches of considerable size, terminating in blunt apices. Seriatopora is much more slender and ramified, the branches terminating in sharp points.
Sect. 2. Fungacea.—This section of Cyclocnemaria contains a number of solitary and colonial corals of very varied form united in the possession of a number of cross-bars called "synapticula" connecting the septa, and thereby giving strength to the calyx apart from any increase in the thickness of the calyx-wall. The family Fungiidae shows many peculiarities which separate it very distinctly from both the Cyclocnemaria and the Aporosa. The Eupsammiidae, however, approach the Cyclocnemaria in many respects, and the Plesiofungiidae form a connecting link with the Astraeidae. It is very probable that this section had a dual origin, and therefore does not represent a single line of descent.
Fam. 5. Plesiofungiidae.—This family is related to the Aporosa in the possession of septa that are generally solid and imperforate, and to the Astraeidae in particular in the possession of dissepiments. They differ from them, however, in the presence of synapticula and in certain peculiarities of the tentacles.
The genus Siderastraea has recently been studied by Duerden.[[419]] The colony is usually massive and encrusting in habit. The zooids when expanded do not rise much above the level of the corallum. The tentacles are short and are arranged in irregular cycles on the disc. They terminate in knobbed extremities, and those of the inner cycles are bifurcated. The colour of S. sideraea is reddish-brown when alive. Siderastraea is found in shallow water on the coral reefs, and is widely distributed.
In Agaricia the colony is more foliaceous. The tentacles are rudimentary or small. The colour of the living zooids is very similar to that of Siderastraea. Epistrelophyllum is a solitary coral, from the Jurassic series, belonging to the family.