PERISTOMATA. MOLLUSCA. PALUDINA. 227 



cylindrical, and so partially in contact as to expose about one 

 half of the cylinder ; the last entirely disjoined from the preced- 

 ing one for at least the half of a revolution ; aperture circular, lip 

 simple and sharp ; on looking at the shell from below, no umbili- 

 cal opening is found ; operculum horny, apex central, elements 

 concentric. Length -yV i»ch, breadth -^^ inch. 



Found at Fresh Pond and other ponds, on stones and sub- 

 merged sticks ; and has been for many years in our cabinets 

 marked as a Paludi'na. 



Animal very active ; head proboscidiform, half as long as the 

 tentacles, bi-lobed in front, dark, terminated with light ; tentacles 

 rather stout, light drab-colored, with a line of silvery dots on the 

 upper side, over the large, black eyes ; foot, tongue-shaped, as 

 long as the first whorl, dilated into two acute angles in front, light 

 drab-color ; respiratory organ occasionally protruded to half the 

 length of a tentacle on the right side. 



This species is widely distinguished from all other described ones by 

 its minuteness, its color, its elongated form, and its want of an umbili- 

 cus ; of which characters the last two seem to arise from the loose 

 manner in which the whorls are united. 



Genus PALUdInA, Lam. 



Shell ovate-conical, whorls rounded ; aperture ovate, acute pos- 

 teriorly^ and modified by the preceding whorl, margin simple ; 

 operculum horny, origin near one edge, elements concentric. 



Paludi'na deci'sa. 



Shell suh-conic, thick and strong, olivaceous ; whorls five, con- 

 vex, covered ivith minute, revolving lines, eroded at tip; aperture 

 ovate, halfithe length of the shell, bluish ivithin; umbilicus none. 



Figure, see Wood-cut, page 144. 



State Coll., No. 61. Soc. Cab., No. 1347. 



Cochlea Virginiana e flava viridescens, non fasciata, Lister ; Conch., t. 27, f. 27. 



Petiver; Gazophyl., t. IIG, f. 18. 

 Paludina decisa, Say ; Mcholson's Encyc, {Jlmer. ed.,) pi. 2, f. G. Amer. Conch , 



pi. 10. 

 Paludina limosa, Vai.enc. ; Recucil d'Ohs. de Zool. ^-c, par Humh. et Donpl, ii. 



253. pi. l,f. 1. 



