Mr. R.J. L. Guppy on new Operculate Mollusca. 248 
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 
sarcosoma, 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 heen indicated in other groups of Corals. It 
leads us to suppose that an analogous arrangement exists 
all the species livg in colonies—that is to say, forming a 
zoanthodema. 
The sarcosoma secretes a viscous and plastic fluid capable of 
agelutinating 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 Letopathes Lamarck was a 
spiculigerous Antipatharian. 
The reproductive organs are developed in the thickness of the 
radiating folds, behind the convoluted filaments, precisely as in 
the Actinie. The sexes are most commonly borne upon distinct 
polyparies ; nevertheless both male and female polypes may 
be met with in the same colony. I have 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 Actiniade 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. Lecumere 
Guppy. 
§ 1. Fluviatile Species. 
Ampullaria purpurascens, n. sp. 
Shell ovate, narrowly perforate, rather thin, subopaque, simply 
horn-coloured, or purplish with numerous indistinct darker 
purple bands; striated by close lies of growth, which are 
crossed at right angles by more distant, mterrupted, low, 
6 
