POST-GLACIAL MOLLUSCA 665 
Galba caperata (Say) 
Caperata is abundantly distributed over the northern half of 
Illinois. The marl specimens are numerous, quite typical, and 
mostly mature. 
Galba obrussa decampi (Streng) 
This characteristic marl fossil is common in the Urbana marl 
deposit. ‘The specimens show some peculiarities of interest. The 
whorls are very heavily shouldered, the sutures almost channeled, 
and the aperture is separated from the body whorl by a deep 
channel, causing the inner and outer lips to become continuous and 
the aperture to become auriform. ‘There is some variation in the 
height of the spire and in the relative width of the shell. The 
collection contains both adult and young shells. 
The Urbana shells give the most southern record for the distri- 
bution of the species; the only recent records from the state are 
in Lake and McHenry counties, and the only fossil record from 
post-glacial deposits is near Chicago. It is known living from a 
number of localities in Michigan, and from Maine, New York, and 
Michigan in marl beds (Baker, 1911, pp. 290-91, pl. 32, figs. 
15-22). It is apparently a Pleistocene species that is dying out, 
being characteristic of the cold climate immediately following the 
retreat of the ice. 
SANGAMON RIVER, NEAR MAHOMET 
The mollusks from this locality occur in a sand stratum four 
feet below the surface. The fauna is distinctively of a fluviatile 
character and not of pond character, as is the case with the Urbana 
marl fauna. The species obtained by Dr. Savage are listed below: 
UNIONIDAE 
Fragments of a river mussel. 
SPHAERIIDAE 
Sphaerium solidulum (Prime) 
Apparently rare. Found throughout the state. 
Pisidium compressum Prime 
A half-valve of this common Illinois species was found. It 
evidently drifted from a more favorable habitat. 
