208 PLANORBIS. 



Subgenus NAUTILINA, Stein. 



21. PLANORBIS VERMICULARIS, Gould. 



Plate 7, fig. 4—6. 



Shell small, dome-shaped, minutely striated 

 by growth, whorls four, the last one deflected 

 near the aperture, rounded at periphery, tip 

 depressed, suture very deep, the whorls slop- 

 ing towards it; base cup-shaped, exhibiting 

 all the whorls. Aperture exhibiting a very 

 oblique section of a cylinder; lip embracing 

 about one-half the height of the last whorl 

 and joined by callus. 



Diam. 5, alt. 1-6 mill. 



Oregon and California. 



It is about the size of PI. defiectus, Say, but 

 is less depressed, the whorls more cylmdrical, 

 not carinated at periphery. 



This is the representative in the Pacific 

 States of our common PI. defiectus, 

 (55) 



