Eastman C. R. Text Book of Paleontology edited by C. R. Eastman adapted from German of K. A. von Zittel, 2nd edition revised and enlarged by the editor in collaboration with the following named specialists: R.S. Bassler, W. H. Dall, C. D. Walcott. Volume 1. MacMillan & Co., London. xii + 839 pp. Internet Archive
William Twenhofel and Robert R. Shrock 1935, Invertebrate Paleontology, McGraw Hill Book Co. New York & London, posted at the Internet Archive as public domain.
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