Mr. R. J. L. Guppy on new Operculate MuUnsca, 243 Gerardia thus approaches Antipathes and Leiopathes; but the number in those genera, never exceeding six, separates it from them generically. The cavity of the body displays the same number of radiating folds, analogous to those of the polypes of other Corals. A very abundant vascular network occupies the whole of the »arcosoma, and opens into the body-cavities of the polypes, which thus communicate with each other. A similar condi-tion was already known to occur in the Alcyonaria, but has not previously been indicated in other groups of Corals. It leads us to suppose that an analogous arrangement exists in all the species living in colonies — that is to say, forming a soanthodema. The sarcosoma secretes a viscous and plastic fluid capable of agglutinating all small bodies which come into contact with it. Thus we find on the surface of Gerardia grains of sand and spicules of Bebryces, Muricea, Gorgonia, and Sponges which live beside it. It is to this, no doubt, that we must refer for the origin of Haime's opinion that his Leiopathes Lamarcki was a spiculigcrous Antipatharian. The reproductive organs arc developed in the thickness of the radiating folds, behind the convoluted filaments, precisely as in the Actinia. The sexes are most commonly borne upon distinct polyparies ; nevertheless both male and female polypes may be met with in the same colony. I hare not seen any herma-phrodite polypes, but it would not be surprising if such should exist. In the form of its polypes Gerardia much more closely resem-bles the Actiniadaj than the Alcyonaria. This approximation^ established by Dana for two species of Antipathes, and accepted by Milne-Edwards and Haime, is therefore confirmed in this case by a minute investigation which cannot leave room for any doubt ; for Gerardia is much more nearly related to the Zoan-tharia than Antipathes. XXVII. — Descriptions of new Species of Fluviatile and Terrestrial Operculate Mollusca from Trinidad. By R. J. Leghmerb Guppy. § 1. FtwriatUe Species^ AmpuUaria pvrpunueens, n. sp. Shell ovate, narrowly perforate, rather thin, subopaque, simply horn-coloured, or purplish with numerous indistinct darker purple bands ; striated by close lines of growth, which are crossed at right angles by more distant, interrupted, lowj 16*
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