PLANOBBIS. 197 
Subgenus ADULA, H. Adams. 
11. PLANORBIS MULTIVOLVIS, Case. 
Plate 6, fig. 1, 2. 
_Whorls seven, about half the last whorl 
overlapping the preceding one, sometimes the 
last whorl suddenly distorted and expanded 
for the last half of its length; right side con- 
cave, left side slightly acuminate and cari- 
nate; throat campanulate; aperture opening 
towards the left, but projecting on both sides 
beyond the preceding whorl. 
Diameter 16 mill. 
Northern Michigan. 
(44) 
