THE NAUTILUS. 113 



Valvata tricarinata Say. 



Valvata tricarinata var. confusa Walker. 

 Valvata bicarinata Lea. 



Valvata bicarinata var. normalis Walker. 



A quantitative study of the Valvata s collected is very interesting. 

 275 specimens were collected, of which 117 were typical tricarinata, 

 104 bicarinata var. normalis, 31 tricarinata, var. confusa, 21 bicari- 

 nata, 1 specimen was 4-carinate and 1 specimen of bicarinata was 

 almost ecarinate. 



The most common forms of the carinate Valvatas would seem to 

 be tricarinata and bicarinata var. normalis ; typical bicarinata seem- 

 ing the rarest. 



Amnicola limosa Say. Common. 



Amnicola walkeri Pilsbry. A single specimen of this very distinct 

 species was found, but a careful search of the lake would probably 

 reveal a number of specimens. It is one of the most characteristic 

 of the fresh-water mollusks. 



Planorbis campanulatus Say. Very common. 



Planorbis bicarinatus Say. Common. 



Planorbis exacutus Say. Apparently rare, as only two specimens 

 were found. 



Planorbis parvus Say. Very common. 



Limncea caperata Say. Fairly common. 



Limntza humilis Say. Not common. 



Pliysa heteroslropha Say. Not common. 



Physa gyrina Say. Not common. 



Succinea, retusa Lea. Common. 



A NEW FLORIDIAN AMNICOLA. 



BY H. A. PILSBRY. 



Amnicola augustina n. sp. 



Shell narrowly umbilicate, brown or olive-brown, smooth, ovate- 

 conic ; spire convexly conic, the apex rather obtuse. Whorls 4|, 

 quite convex, separated by deeply-impressed sutures. Aperture 

 about half as long as the shell, broadly ovate, obtusely angular above; 

 peristome acute, continuous, dark-edged, adnate to the preceding 



