INTRODUCTION. 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, Ia., 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. VII. of the Mlinois 
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. 8. A. Miller favored us with the loan of his valuable types of 
Lower Silurian species. Mr. E. O. 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. 8. 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- 
