PLANORBIS. 191 
3. PLANORBIS TUMENS, Carpenter. 
Plate 5, fig. 5, 6. 
Shell rapidly swelling, small, horn or red- 
dish smoke-colored; whorls four or five, with 
light waving strie; sutures deeply impressed ; 
on one side subangulate or subcarinate near 
the suture, on the other rounded; umbilicus 
very deep; aperture with a sinuous edge, one 
side standing out above, flattened below, the 
other flattened above, produced below, capa- 
cious and rounded; labium very thin. 
Diam. 15, alt. 6°5 mill. 
Mazatlan, Lower California, Southern Cali- 
fornia. 
The irregularity of the last whorl, as shown 
in my figures, appears to be characteristic of 
the species. 
(38) 
