INTEODUCTION. 7 



It is especially difficult for us to express our obligations to Mr. Victor 

 W. Lyon, of Jeffersonville, Ind., who with the utmost liberality placed his 

 own collection at our disposal, and also that of his father, the late Major 

 Sidney S. Lyon, through which we secured the use of all the types of the 

 species described by Major Lyon himself, and by Lyon and Casseday. 



Mr. Lisbon A. Cox, of Keokuk, La., gave us access to his extensive 

 and unique collection from the Keokuk limestone, containing the types of a 

 large number of species described by Worthen in Vol. YII. of the Illinois 

 Reports. 



Mrs. Yandell, of Louisville, Kentucky, has sent us for examination some 

 rare types in the collection of the late Dr. L. P. Yandell. We tender our 

 special thanks to this venerable lady for the efforts she made to serve us. 



To the naturalists and collectors of Cincinnati and vicinity we are 

 indebted for great facilities in studying the crinoidal fauna of the Lower 

 Silurian of that region. Mr. I. H. Harris, of Waynesville, Ohio, placed at 

 our disposal the species of his magnificent collection of Hudson River Cri- 

 noids. Mr. S. A. Miller favored us with the loan of his valuable types of 

 Lower Silurian species. Mr. E. 0. Ulrich, of Newport, Ky., has sent us for 

 examination the types of his species, and besides other instructive speci- 

 mens. He also used his influence in our behalf with Messrs. Oeh and 

 Vaupel, who placed some of their finest specimens in our hands. 



Dr. E. N. S. Ringueberg, of Lockport, N. Y., has sent us the types of 

 his species of the Niagara group of Western New York, with liberty to use 

 them as we might find desirable. 



To Prof J. M. Clarke, of Albany, N. Y., we are indebted for the use 

 of valuable type specimens from the Hamilton group of New York, then in 

 his private collection, but since passed into the New York State Cabinet. 



Mr. Thomas A. Greene, of Milwaukee, Wis., placed in our hands a 

 large collection of natural casts from the Niagara group, including types of 

 the Waukegan species ; and Mr. W. C. Egan, of Chicago, a similar collection 

 from near Chicago, containing the types of the species described from that 

 locality. 



Mr. F. A. Sampson, of Sedalia, Mo., gave us the use of his collection, 

 containing the types of a large number of species described by S. A. Miller 

 in the Missouri and Indiana Reports ; and Prof. R. R. Rowley, of Louisiana, 

 Mo., furnished us the types of his species. 



We are also indebted for the use of specimens and friendly acts in vari- 



