Evidence on the Deposition of Loess.— Owen. 2g7 
If only a few of the "alternata" retained the vivid flamings 
their testimony might, possibly, be regarded as of doubtful 
value, bvit since they may easily be collected by thousands and 
faded specimens are rare, it would appear quite safe for the 
advocates of the aqueous theory to find a little solace in them, 
as well as the casts, and accept both for a very tangible sup- 
port of their case. i 
A small collection of fossils from the same sources had 
previously been sent to Dr. Theodore Gill for his identification. 
None of the flaming alternata'weTe included. He referred the 
shells to professor Bartsch to determine exactly, and returned 
them with the report rendered and the assurance that all the 
species are living land shells, although some of the Succineas 
are "very like fresh-water limnseids." The species reported 
are: Circinaria concava Say; Polygyra multilineata Say; Suc- 
cmea avara Say; Succinea grovenorii Lea; Succinea lineata 
Lea. 
The specimens submitted by professor Wright were mainly 
taken from greater depths in the blufif than those of the other 
two collections. , 
The Circinaria concava and the Succinea avara are by no 
means so abundant as the other forms, while the Succinea ob- 
liqua is the most numerous everywhere and is found at greater 
depths than any other form in cuts that penetrate far into the 
bluff or through it, and they are now living in shallow water 
in the deep ravine north of the fossil bearing hills, but not else- 
where in that vicinity. Yet in the highest portions of the up- 
land loess the Patula alternata and others of the lists given are 
everywhere associated with it and are of almost equal num- 
bers. 
These high elevations are doubtless the land areas which 
produced the terrestrial mollusks, — when the waters were not 
at flood stage. It is reasonable to suppose that then as now 
there were, within certain limits, considerable variations as to 
time, duration and stage of the annual flood; these being de- 
pendent upon such variable conditions as the amount of both 
-winter snow-fall and spring rains, and very largely on the di- 
rection of the winds. If the winds persist in the north until 
late spring the "]\in& rise" must bring "extreme high water" 
of short duration but so late as to destroy early vegetation on 
