^,,i PREFACE. 



friendsliip a.ul intiniiite correspondence relating to scientific questions, and 

 especially to the Brachiopoda. The pages and illustration of this volume will 

 bear testimony to the knowledge derived from this eminent source. Also to 

 Dr. Th. Tschernyschew and Dr. Fr. Schmidt, of St. Petersburg, Russia; to 

 Prof. E. Kaysee, of Marburg, Germany ; to Miss Agnes Crane, of Brighton, 

 England : Dr. D. P. ffinLERT, of Laval, and Prof. Charles Barrois, of Lille, 

 Friuice ; to Dr. G. Lindstr()M, of Stockholm, Sweden, and to Mr. John Young, 

 of Glasgow, Scotland, acknowledgments are especially due. 



The lithographic plates accompanying this work have been drawn on stone 

 by Mr. Philip Ast, whose accurate and artistic execution of similar work is 

 already known to the students of these volumes. The original drawings of the 

 earlier plates were mostly made by Mr. R. P. Whitfield and the late Mr. F. B. 

 Meek ; the drawings for the later plates was begun by Mr. E. Emmons, whose 

 services were subsequently supplemented by the skillful and beautiful work of 

 Mr. George B. Simpson. 



To Mr. Charles Schuchert, my private assistant, this volume owes much. 

 His critical knowledge of the species of American Brachiopoda, and his famil- 

 iarity with the literature pertaining to them, as well as his unequaled collec- 

 tion of fossil Brachiopoda, have all been placed at the disposal of the work with 

 the devotion characteristic of the student. To him is due the fullness of the 

 bibliographic tables, which afford virtually a complete summary of American 

 literature upon these genera. 



To Prof. John M. Clarke, Assistant Palaeontologist, I am especially indebted 

 for his faithful and appreciative devotion to the accomplishment of this under- 

 taking. On the resumption of this work in 1888, Mr. Clarke was appointed 

 my official assistant, and he entered at once into sympathy with my plan, and 

 became an enthusiast in the study of the Brachiopoda. To him I am indebted 

 for carrying out in its details, the spirit of my conception to a degree of com- 

 pletion which I had not anticipated. 



JAMES HALL, 

 Albany, May, 1892. State Geologist and PalcRontologist. 



