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The Nautilus. 



Vol.. XX. SEPTEMBER, 1006. No. 5. 



TWO NEW AMERICAN GENERA OF BA80MMAT0PH0RA. 



BY HENRY A. PILSBRY. 



In the course of a collecting expedition to Alabama in October 

 and November, 1903, Mr. A. A. Hinkley found a number of mol- 

 lusks of unusual interest and importance. 1 Among them were two 

 species of spiral-shelled gastropods quite unlike any fresh-water 

 snails hitherto known in this country, having affinities with the 

 Ancylidce. 



Like Ancylus, the new forms are essentially sinistral in their soft 

 parts, but the shells are dextral. They are very small snails, and 

 were found on or usually under rocks in swift water, and evidently 

 do not depend upon free air for respiration, having a false gill in the 

 pallial chamber. 



Genus Amphigyra nov. 



The shell is minute, Neritoid or Crepidula-like, with a small 

 depressed lateral spire, apparently dextral, composed of about 1^ 

 very rapidly enlarging whorls, the last very convex dorsally, im- 

 perforate ; the apex is smooth, and the last whorl is spirally striate. 

 The aperture is very large, oblique, transversely oval, the peristomi 

 continuous and free, thin. Cavity of the spire very small, a thin, 

 broad, concave columellar plate projecting across the end next the 

 spire, as in Crepidula or Latin. 



The soft parts are sinistral, externally Limna*oid, with large 

 black eyes near the inner bases of the short blunt cylindric tentacles. 



'See lists of the species collected, in NAUTILUS for August and September, 

 1904. 



