SUGGESTIONS FOR FUTURE STUDY 403 



River, in the region of the overlap of the Kansan and Illinoian drift sheets, 

 both the Yarmouth and the Sangamon intervals may be studied. Much work 

 remains to be done in northwestern Illinois, where many deposists occur con- 

 taining the remains of this ancient life. Leverett's maps in his "Illinoian 

 Glacial Lobe " will be found of great assistance in this connection. 



Indiana and Ohio 

 In many parts of these states, the old forest bed, which is believed to be of 

 Sangamon age, is conspicuously present and may be studied with great advan- 

 tage. Along the Ohio and its tributaries, many good sections occur showing 

 the relation of this forest bed to the overlying and underlying strata. In the 

 northern portion of Ohio, especially along the shore of Lake Erie, it is believed 

 that interglacial deposits occur, and sections should be studied and published 

 confirming this statement. For this work, Leverett's report on this region 

 will be found indispensable. 14 



South Dakota, Minnesota and Wisconsin 

 These states, being covered for the most part by Wisconsin drift, afford 

 splendid opportunities for the study of glacial phenomena. Old soils as well 

 as old lake and swamp deposits should occur beneath this till. Winchell's 

 Final Reports 15 contain man}' good maps of this region. The Driftless area in 

 these states should also be carefully studied, to ascertain if possible the age of 

 the fauna contained in the limestone crevices and beneath the loess de- 

 posits bordering the Mississippi River. 



RELIABILITY OF DATA 



Too strong an emphasis cannot be placed on the admonition to use the 

 greatest amount of care in studying and reporting data of this character. 

 Accuracy of detail is absolutely essential. In making sections, every variation 

 no matter how small, should be noted on a chart, and any material obtained 

 should be correspondingly labeled and carefully preserved for future reference. 

 The character of overlying and underlying till, if these are thot to be present, 

 should be established with reasonable certainty. 



It is eminently desirable that all material collected and upon which deter- 

 minations have been made, should be deposited in some well-known and acces- 

 sible museum, that it may be available for study by subsequent workers. By 

 this precaution previous errors of identification may be corrected. Many times 

 changes of nomenclature cause confusion in interpreting older records; also 

 composite species, later broken up into several species, perplex the subsequent 

 investigator. In short, the greatest effort should be made to make the story 

 of Pleistocene life as true and complete as possible. 



" Monograph, No. XLI, U. S. Geo]. Surv. 



u Minnesota Geological and Natural History Survey. 



