124 
IOWA ACADEMY OP SCIENCE 
But fossils are abundant in the corresponding loess along the Iowan border 
and we have no reason to believe that this is genetically different from the loess 
of the paha and larger Kansan islands. 
These fossils are widely distributed in the loess. With few exceptions they are 
species now abundantly inhabiting the same area. Their terrestrial habits are 
well-known and readily ascertained. In their distribution they bear a clearly 
defined relation to the modern fauna, made up, let it be clearly understood, of 
the same ’species. They give us the only definite tangible clue to the conditions 
whicfi existed during the deposition of the loess, and their evidence cannot be 
suppressed by slighting references to “small molluscan shells,” or by being 
wholly ignored. 
These shells prove the presence of large land surfaces and an abundant 
terrestrial vegetation. Where could they have found such conditions in MgGee’s 
and Norton’s largely ice-covered areas? There is absolutely nothing in this 
fossil fauna to suggest glacial or sub-arctic conditions; and there is nothing in 
it to suggest the presence of large bodies of water. 
On the contrary, the shells offer indisputable proof that the conditions under 
which the deposit in which they occur was formed were not essentially different 
from those which prevail in the same regions today. Indeed, they point rather 
to a somewhat drier climate, as shown by several species identical or affiliated 
with those of the dry western regions, such as OreoheUx ioensis, Pupa muscorum, 
Succinea grosvenorii, Pyramidula sliimekii and SpJiyradium edentuluTU alticoTa, 
and by the depauperation of such species as Succinea ovalis, Polygyra multili- 
neata, Helicina occulta, etc. 
McGee, basing his conclusions on Call’s erroneous deductions, argued that 
these depauperate forms indicate a cold climate. But corresponding depaupera- 
tion may be observed in the modern representatives of these same species as we 
go westward from the moister eastern regions to the drier sections of the 
west, while no such depauperation is noticeable in northerly forms of those 
species which extend northward. It may also be added that this fauna does 
not extend far enough northward to reach climatic regions like those called for 
by McGee’s hypothesis, and that several of the species found in the loess of the 
southern states are subtropical, and do not even extend into our northerly 
temperate regions. 
The depauperation suggests merely a short growing season, the length of 
which was probably limited by drouths. 
It is useless to consider the loess a glacial deposit, or one formed in large 
bodies of water, so long as the presence of these shells is not explained on ra- 
tional grounds consistent with the conditions called for by these hypotheses. 
Absolutely no such explanation has yet been offered by the opponents of the 
aeolian hypothesis, and the latter still stands as the only hypothesis consistent 
with the ecological and faunal conditions which are involved. 
1 ' 
