PALUDINA. 



TESTA ovata vel oblonga, spira subturrita,. 

 anfractibus rotundatis, laevibus, apertura ellip- 

 tica, peritremate continiio, aciitiusculo ; oper- 

 culo corneo, concentric©, nucleo sublaterali. 

 Animal viviparum* 



Placed among the Helices by Linnean writers, but sepa- 

 rated from them by later authors, for very sufficient 

 reasons. A remarkable circumstance in the natural history 

 of this Genus has brought it under the notice of numerous' 

 writers, some of whom have named it from that circum- 

 stance *' Vivipara." It has also been called Cyclostoma, 

 although it is in every respect perfectly distinct from that 



Genus. . i. r. 



The usual form of the species of this f^enus varies 

 from ovate to somewhat oblong, occasionally they are 

 very short; the spire is for the most part somewhat 

 turrited with rounded smooth volutions, but occasionally 

 the spire is very low, and the volutions are more or les& 

 strongly keeled : the aperture is generally elliptical, slightly 

 modified on the inner side by the gibbosity of the last 

 volution ; and somewhat acuminated at the upper part. 

 The operculum is horny, with concentric lines of grovvth 

 and a sublateral nucleus. The animal, in all the species 

 we know, is viviparous, the shells being fully formed 

 before they are ejected from the ovary. Such are the 

 characters of the true PaludincB, and by attention to them, 

 it will not be difficult to distinguish them from those other 

 Genera to which they are most nearly allied,^as Cyclostomay 

 Valvata and Amputlaria. From Cyclostoma ^r\& Valvata 

 whose opercula are spiral they may at once be known 

 by their having a concentric operculum ; but from the 

 AmpuUarice they are only to be distinguished by their 



