514 MORRIS M. LEIGHTON 
planes widened by solution. At the quarry, several solution 
channels are well exhibited and the faces of the rock along the joints 
are in some instances coated with travertine, and in others with 
silt or clay which has been carried down from the surface. The 
clogging of these subterranean channels would give rise to ponds 
in the surface sinks, modern examples of which occur a short 
distance north of Plant No. 3 of the Mississippi Lime and Material 
Company. Such situations may have existed during the Pleisto- 
cene, and if so, offered favorable conditions for the entrapment of 
the region’s fauna of both water and land species. 
The fossil fauna, according to Baker, contains certain elements 
which suggest the arctic phase of a glacial epoch and other ele- 
ments which belong to the warm phase of an interglacial epoch. 
The remains, however, could not have lain on the drift during the 
long period of weathering which followed the deposition of the 
drift. Hence, it is thought the remains of the arctic elements are 
a record of the life which lived in the latter part of the next glacial 
epoch, while the remains of the warm fauna represent the life which 
lived at the beginning of the interglacial epoch following that glacial 
epoch. As the melting of the ice sheet was a response to the 
change of climate from cold to warm, it is believed that with the 
local disappearance of the ice sheet, the warm interglacial fauna 
succeeded the arctic before the deposition of the reddish loess. 
If the till proves to be Kansan in age, the weathering of the 
drift may be credited to the Yarmouth interglacial epoch, the 
mammalian fauna to late Illincian and early Sangamon times, 
the reddish loess probably to the Sangamon, and the buff loess to 
the Iowan. If, however, the till is Illinoian, then the fauna 
probably is a partial record of the life of the latter part of the 
Iowan glacial epoch and the early Peorian interglacial epoch. 
In the latter case, the writer finds some difficulty in assigning both 
loesses to the Peorian, or in referring the upper buff loess to post- 
Wisconsin times. However this may be, the Illinoian and Sanga- 
mon epochs are post-mid-Pleistocene, from the standpoint of the 
duration of the Pleistocene, and the fauna represented by the 
McAdams collection may be regarded as post-mid-Pleistocene. 
