78 CONCHOLOGIA CESTRICA. 
Animal, rostrum produced; tentacles cylindrical ; 
eyes sessile, at their extreme bases; mantle simple in 
front; gill exposed, plumose, lamina pinnate, twisted, 
protected by a respiratory lobe; foot bilobed in front; 
operculum corneous, spiral. 
Genus VALVATA, O. F. MULLER, 1774. 
Shell, sub- discoid, or conoid, umbilicated, thin; 
whorls cylindrical, or keeled; peristome circular, con- 
tinuous. 
V. tricarinata, SAY. 
Cyclostoma tricarinata, Say, Jour. Acad. Phila., L., 
1S7. 
V.tricarinata, Hell, with three whorls, and three prom- 
[W.G.B] inent carina, or revolving lines, one of 
Fig: 161. Which is on the upper edge, one on the 
EH lower edge of the whorl, and one beneath 
the base; suture canaliculate; umbilicus 
large. W. 5, mill. 
Station, Schuylkill River, and tributaries. Chester 
County ; abundant. 
Operculum of V. Lingual Dentition of V. tricarinata. 
tricarinata, [W. G. B.] 
[W. G. B.] Fig. 163. 

Oss. — The ova are deposited from May to midsum- 
mer, in globose, gelatinous masses, of 10 to 30, and of 
a green color; these are hatched in fourteen or fifteen 
days; like Limnea, and Physa, they possess the power 
of swimming in an inverted position, along the surface 
of water. 
