THE NAUTILUS. 113 



Valvata tricarinata Say. 



Vulvuta tricarinata var. confusa Walker. 



Valvata hicarinata Lea. 



Valvata hicarinata var. normalis Walker. 



A quantitative study of the Valvatas collected is very interesting. 

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

 104 hicarinata var. normalis, 31 tricarinata var. confusa, 21 hicari- 

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

 almost ecarinate. 



The most common forms of the carinate Valvatas would seem to 

 be tricarinata and hicarinata var. normalis ; typical hicarinata 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. 



Planorhis bicarinatus Say. Common. 



Planorbis exacutus Say. Apparently rare, as only two specimens 

 were found. 



Planorbis pai-vus Say. Very common. 



Limncea caperata Say. Fairly common, 



Limncea huniilis Say. Not common. 



Physa heterostropha 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 



