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* 



