o mTEODUCTIOK 



ous ways to Mr. Asa S. Tiffany, of Davenport, Dr. C. C. Washburn, of Wal- 

 dron, Ind., Dr. Moses Elrod, of Hartsville, Ind., Rev. H. Herzer, of Berea 

 Ohio, Rev. John Davis, of Louisiana, Mo., Mr. D. H. Todd, of Kansas City 

 Mo., Mr. G. M. Nickels, of Sparta, 111., Mr. E. Brown, of Belfast, N. Y., and 

 others. 



To Dr. Horace G. Griffith, formerly of Burlington, now of Philadelphia 

 we express our grateful acknowledgments for his intelligent and unremitting 

 efforts to aid us in the prosecution of this work, and for his steadfast devo- 

 tion to our interests manifested upon every occasion. 



We also bear in kindly remembrance our former townsman, Mr. James 

 Love, whose fine collection was always at our disposal, and which, together 

 with one made by Mr. J. W. Giles, afterwards passed into our hands. 



Dr. Charles R. Keyes has at all times exhibited a lively interest in the 

 progress of our work, and we owe to him not only the procurement of some 

 valuable specimens, but other friendly offices. 



Nor do we forget our good friend, Orestes St. John, whose keen eye and 

 rare judgment, and no less his skilful pencil, have always been at our ser- 

 vice. We have from him some unsurpassed structural drawings, and he 

 presented us several unique Crinoids from the Coal Measures of Kansas. 



Our thanks are due to Mr. Wm. F. E. Gurley, of Danville, 111., for the 

 use of specimens from Waldron, and to Mr. A. C. Benedict, of Indianapolis, 

 for the use of specimens obtained by him at St. Paul, Ind. 



In addition to the facilities above mentioned, we have had during the 

 preparation of this work our own collection, which contains authentic speci- 

 mens of nine-tenths of the species of Crinoids described from the United 

 States, and two-thirds of all the European species. From many of the typical 

 localities we have been able to obtain, either by purchase of local collections, 

 or by personal exertions, large series of speciniens, by means of which it has 

 been possible to study in many cases, and among different genera, the indi- 

 vidual variation existing in the limits of a species, and the modifications due 

 to growth. 



In looking over the descriptions it will probably surprise some of the 



authors to find so many of their species placed in the synonym lists, but 



we were obliged to do so after careful study and comparison with authentic 



specimens. 



CHAELES WACHSMUTH. 



FEANK SPEINGEE. 

 Burlington, Iowa, May 1, 1894. 



Received at Cambridge, September 1, 1894. 



ALEXANDER AGASSIZ. 



