The writers' study of the Belt series began in 1927 and was continued in 1928 and 1932. Field work was virtually completed in 1934, when a grant from the Geological Society of America financed twelve weeks in Glacier and Waterton Lakes national parks and visits to other Belt outcrops. Further study of rhythmic sedimentation and algal deposits was permitted by a second grant from the Geological Society in 1936. The writers acknowledge their debt to the Society, to officials of the National Park Service, and to Dr. Charles Deiss, who lent specimens from Montana localities.
Collections of 1927 and 1928 are in the University of Cincinnati Museum; those of 1934 and 1936 were sent to Princeton University; specimens collected by Dr. Deiss are at the University of Montana. Series of metatypes have been placed in the Carnegie Museum, the Paleontological Museum of Oslo, the Naturhistorisches Museum, Vienna, and other . . .