238 
IOWA ACADEMY OF SCIENCE 
in g them but suggesting no explanation or significance of their 
presence. 
But the most remarkable effort of those who, appreciating the 
need of an explanation of the presence of the terrestrial forms, but 
still adhering to the aqueous hypothesis, appears in the attempted 
explanation of the presence of the terrestrial shells in the loess 
offered by Prof. J. E. Todd, who strives to show that the surface 
shells were dropped into crevices, or were covered by the creeping 
of the loess, and were not contemporaneous with it. This explana- 
tion was first suggested by Professor Todd in the report of the 
Missouri Geological Survey.* It was again presented by the same 
author before this Academy Dec. 29, 1897, in a paper entitled 
“The Degradation of the Loess,” but it was so thoroughly demol- 
ished in the subsequent discussion by Professor Calvin and others, 
that that portion of the paper containing the attempted explana- 
tion was withdrawn from publication, and does not appear as a 
part of that paper printed in the Proceedings of this Academy, f 
Without submitting further evidence Professor Todd now comes 
with a repetition of this explanation in a paper read by title at the 
last meeting of this Academy.}; In the Missouri report, Professor 
Todd simply refers to “the fossils which have been introduced 
extensively in the creeping and cracking of the deposit.” 
But in the more recent paper, he attempts to present a more 
complete statement of his view, which however, does not materially 
differ from the presentation of nine years ago, as the writer recalls 
it. He bases his view on the following observations and opinions : 
First, the loess along the Missouri river shows frequent slipping 
and step-faulting. Second, most of the fossil localities are on hill 
sides and near streams. Third, the shells were gently entombed by 
the creeping loess. 
It is evident that Professor Todd has limited his observation 
largely to the immediate vicinity of the Missouri river, otherwise 
he would scarcely have set forth the first two of these propositions 
as characterizing all loess. Step-faulting is indeed common along 
the Missouri, and also the Mississippi, especially on the eastern 
side. If fossils were limited to the steep slopes which are most 
subject to this creeping and faulting, there might be some reason 
in this contention. But unfortunately for. Professor Todd’s view, 
innumerable examples of fossiliferous loess occur in localities and 
* Vol. X, p. 129, 1896. 
t Vol. V, pp. 46-51, 1898. 
I See Proceedings, Vol. XIII, pp. 187-194, 1907. 
