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 Pl. deflectus, Say, but 
is less depressed, the whorls more cylindrical, 
not carinated at periphery. ; 
This is the representative in the Pacific 
States of our common Pl. dejlectus, 
(55) 
