No obstacle has presented itself more persistently in the way of those who have attempted to explain the formation of loess deposits by aqueous or glacial agencies, than the presence of the remains of strictly terrestrial mollusks in the deposits.
Proceedings of the Iowa Academy of Science
©1907 Iowa Academy of Science, Inc.
"The Loess of the Missouri River,"
Proceedings of the Iowa Academy of Science, 14(1), 237-256.
Available at: https://scholarworks.uni.edu/pias/vol14/iss1/21