1881.] Geclogy and Paleontology. 585 
GEOLOGY AND PALASONTOLOGY. 
Fossits OF THE Iowa Logss.—The loess of Iowa is, for the 
major part, limited to the extreme western and south-western 
portions of the State. The counties of Fremont and Mills are 
entirely, while those of Page, Pottawattamie, Harrison, Monona 
and Woodbury, are partially covered by this deposit. Professor 
Witter has discovered it under and about the city of Muscatine, 
on the Mississippi river, but as the following list is the result of 
personal observations, it will be limited to those portions studied 
formation, was all deposited during the same period, had the 
Same origin, and the geographical extent of its deposition is too 
limited, by far, to admit of such radical differences of climate that 
tropical and sub-tropical forms should be found on one side of 
the M issouri river, but fail to appear in the same formation on the 
Opposite side. 
During occasional visits to the bluffs of loess that border the 
Missouri in the counties of Fremont and Mills, the following 
Species of Mollusca have been found, some of them in fair abund- 
ance when the nature of the deposit is considered, while others 
are of extreme rarity: Hyalina arborea Say, H. indentata Say, 
1. minuscula Binney, Stenctrema monodon Rack., Helitodiscus line- 
atus Anth., Conulus fulvus Drap., Strobila labyrinthica Say, Patula 
alternata Say, P. striatella Anth., Mesodon clausa Say, M. pro 
funda Say, M. multilineata Say, M. thyroides Say, M. albolabris 
Say, Vallonia pulchella Mill., Macrocyclis concava Say, Pupa 
Pentodon Say, P. armifera Say, Succinea obliqua Say, S. ovalts 
y, and perhaps one or two other species of Pupa not satisfactorily 
determined, This list comprises all the land shells found. The 
