212 PLANORBIS, 
ee, 
28. P. CIRCUMSTRIATUS, Tryon. 
Plate 7, fig. 14—16. 
Shell small, rugose, generally distorted in 
adult specimens, (the whorls not proceeding 
in the same plane, but elevated or depressed 
from it at times); volutions four, convex, 
increasing very slowly in diameter, with 
deeply impressed suture, towards the aperture 
deflected; below concave, but exhibiting all 
the volutions, with two or three raised revolv- 
ing lines; aperture small, very oblique. Light. 
horn color. 
Diameter 6 mill, height 1:5 mill. 
Artificial pond at Weatogue, Connecticut. 
The remarkable raised revolving lines are 
visible on the under surface of all the adults I 
have examined, but on the young shells there 
are no traces of them. . 
For the remarkable circumstances con- 
nected with the discovery of this species, ref- 
erence is made to the description of Limnea 
Shurtlefit in this work. 
(59) 
