THE LOESS OF THE MISSOURI RIVER. 
BY B. SHIMEK. 
No obstacle has presented itself more persistently in the way of 
those who have attempted to explain the formation of loess de- 
posits by aqueous or glacial agencies, than the presence of the 
remains of strictly terrestrial mollusks in the deposits. 
At first the advocates of the aqueous and glacial theories at- 
tempted to brush aside the entire question by mere reference 
to “land and fresh-water shells” in the loess, or specifically sought 
support for their contentions in the presence of the few fresh-water 
forms which occur in the deposit. 
But when it was demonstrated beyond question that the vastly 
preponderating proportion of the shells consists of strictly terres- 
trial forms, and that the relatively scant fresh-water species are 
all inhabitants of small ponds or pools, and that no fluviatile 
species occur, many of the former advocates of the aqueous theory 
abandoned or modified their earlier views. But there remained 
those who still sought solace in the presence of the few fresh- 
water forms, and one positively declared* that “many land forms 
may exist in an aquatic formation, but the existence of a single 
aquatic fossil in the loess requires the presence of water.” 
Another, confessedly unfamiliar with the subject, misinterpret- 
ing, and through this lack of familiarity misrepresenting the state- 
ments of competent conchologists, has questioned the correctness 
of the present writer’s identification of the terrestrial shells, and 
suggested that they may be fresh-water forms, f 
Still other writers X have adopted the comfortable method of 
simply disregarding the presence of the fossils, or barely mention- 
* Annual address of President N. H. Winchell: Bull Geol. Soc. of Am., vol. 14, p. 145, 
Agr. , 1903. 
t Miss Luella A. Owen, Am. Geologist, Vol. XXXIII, pp. 223-228, Apr., 1904, and Vol. 
XXXV, pp. 291-300. The former paper has been noticed by the writer in the Bull. Lab. Nat. 
History, State University of Iowa, Vol. V, pp. 369-381. In the second paper the statements 
of Dr. Gill and Mr. Gratacap were not given in their correct relation to the question, as the 
writer ascertained by direct and indirect correspondence, and Miss Owen’s argument, 
based on a misconception of these statements, is wholly without value. 
t As, for example, Prof. W. H. Norton in the reports of the Iowa Geol. Survey on the 
Geology of Linn (Vol. IV), Scott (Vol. IX) and Bremer (Vol. XVI) counties. 
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