HISTORICAL SKETCH. liii 



In the introduction to part 2 the reader will find further discussion of the stratigraphic 

 peculiarities and the distribution of the fossils of the Lower Silurian, and some compari- 

 tive tables indicating the relations of the Mississippi valley with the same rocks in New 

 York and Canada and in the Cincinnati region. 



Dates of publication of the chapters of this part of this volume. 



The five chapters which are included in part i were published, in editions of one hun- 

 dred copies each, and distributed on the dates given below. 



Chapter I. Cretaceous Fossil Plants from Minnesota. Feb. 15, 1893. 



Chapter II. The Microscopic Fauna of the Cretaceous in Minnesota, with additions 

 from Nebraska and Illinois. Feb. 15, 1893. 



Chapter III. Sponges, Graptolites and Corals from the Lower Silurian of Minnesota. 

 June 6, 1893. 



Chapter IV. On Lower Silurian Bryozoa of Minnesota. Jan. 15, 1893. 



Chapter V. The Lower Silurian Brachiopoda of Minnesota. June 6, 1893. 



ACKNOWLEDGMENTS. 



The authors of part I of Volume in are under obligations to numerous geologists for 

 advice and cooperation. Throughout the whole course of its preparation they have enjoyed 

 the friendly aid and guidance of Mr. W. H. Scofield, late of Cannon Falls, whose familiar- 

 ity with those formations in Goodhue and Olmsted counties has not only brought to light 

 many fossil forms but has enabled the authors to study in the field their stratigraphy with 

 greater fullness. Prof. James Hall generously allowed the use of advance proofs of his 

 recent revision of the Brachiopoda (Paleontology of New York, vol. viii, part 1. ) A year 

 or more before the publication of that volume. 



For various favors the authors also have to thank Mr. C. D. Walcott, C. E. Beecher, 

 Prof. J. M. Clarke, Prof. A. Hyatt, J. F. Whiteaves of the Canadian Geological Survey, 

 Capt. A. W. Vogdes, Prof. C. W. Hall and Mr. F. W. Sardeson. Throughout the volume 

 will be found various acknowledgments for fossils and other aid furnished. 



