THE NATURAL HISTORY SURVEY. 309 



vex; color varying from light horn to greenish; sculpture con- 

 sisting only of fine growth lines (Fig. 108); sutures impressed, 

 margined by a white line which is frequently bordered by a 

 dark chestnut line; protoconch consisting of one whorl, which 

 is smooth and varies from porcelain-white to rather dark horn 

 color; aperture rather large, oval, occupying from two-thirds to 

 three-fourths of the length of the entire shell; peristome thin, 

 acute, thickened on the inside by a whitish or bluish callus, 

 which is bordered on .the inside with red; columella almost 

 straight, with a whitish callus which is sometimes lined with 

 red. 



Animal: Similar to that of gyrina. 



FIG. 108. 

 Surface sculpture of PHYSA HETEROSTROPHA Say. (Original.) 



Jaw and Radula: In all respects like those of gyrina. 



Genitalia: Not observed. 



Distribution: Eastern and Southern States; Maine to 

 Georgia and west to Michigan and Illinois; Southern Canada. 



Geological distribution: Pleistocene; Loess. 



Habitat: In ponds and streams, adhering to sticks and 

 stones and crawling over the muddy bottom. 



Remarks: During a visit to the Philadelphia Academy of 

 Sciences some time ago, Mr. Pilsbry called the writer's atten- 

 tion to the fact that heterostropha had a smooth shell, while 

 gyrina and some others had a shell with raised (or, as the writer 

 would describe them, impressed) spiral lines. Following up 

 this suggestion a large number of Physce have been examined 

 with the result that instead of there being two species in the 

 present area, as was at first supposed, there are four, with one 

 or more varieties. Heterostropha is an annuan, attaining full 

 maturity in one year. 



