PREFACE. 
IX 
together for such an important purpose as a monograph of the Paleozoic 
Ckustacea. 
In taking leave of a work which has in the past occupied his mind and 
prompted his earnest endeavors, he can only regret that the circumstances 
attending its final production have been less felicitous than he could have 
wished. 
In the preparation of the matter for the press, and in the critical study of 
the material, the author acknowledges with great satisfaction the able and 
untiring efforts of his assistant, Mr. John M. Clarke. 
The author acknowledges the liberality with which specimens have been 
placed at his disposal for study and comparison, and begs leave to express his 
obligations to the following-named gentlemen and institutions: 
Dr. J. S. Newberry, __ __ __ .. New York, N. Y. 
Mr. Louis Bevier, __ __ __ __ __ Marbletown, N. Y. 
Mr. Cornelius Van Gaasbeck,_ _ __ __ __ Kingston, N. Y. 
Prof. S. G. Williams, . _ __ Ithaca, N. Y. 
Prof. H. S. Williams, __ __ __ Ithaca, N. Y. 
Prof. J. F. Whiteaves, Geological Survey of Canada, Ottawa, Canada. 
Mr. R. D. Lacoe, __ __ __ __ __ Pittston, Penna. 
Prof W. H. Barris, __ __ __ __ Davenport, Iowa. 
Mr. D. S. Chatfield, _ _ _ _ _ . . . _ _ Syracuse, N. Y. 
Mr. A. 0. Osborne, __ __ Waterville, N. Y. 
Mr. D. D. Luther, __ __ __ __ Naples, N. Y. 
Dr. C. Rominger,_. __ __ __ Ann Arbor, Mich. 
Sir William Dawson, .. __ __ __ Montreal, Canada. 
Prof B. K. Emerson, ... __ ... __ Amherst, Mass. 
Mr. Charles E. Beecher, __ .. New Haven, Conn. 
National Museum, __ __ __ Washington, D. C. 
American Museum of Natural History, __ New York, N. Y. 
Prof. J. P. Lesley, _ __ __ __ .. Philadelphia, Penna. 
Prof R. P. Whitfield,. _ New York, N. Y. 
Dr. J. Pohlman, __ __ .. __ __ Buffalo, N. Y. 
Prof George H. Cook, _ __ __ __ New Brunswick, N. J. 
Prof. S. Calvin, __ __ __ __ __ Iowa City, Iowa. 
