THE NAUTILUS. 



Vor,. XX. SEPTEMBER, 1OO6. No. 5. 



TWO NEW AMEBICAN GENERA OF BA80MMATOPHORA. 



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- 

 Insks 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 

 Ancytidce. 



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 l 

 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 peristome 

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

 broad, concave columellar plate projecting across the end next the 

 spire, as in Orepidula or Latia. 



The soft parts are sinistral, externally Limnseoid, with large 

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



l Seo lists of the species collected, in NAUTILUS for August and September, 

 1904. 



