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INTRODUCTION. 
To Dr. G. Hambach of St. Louis we owe the facility of examining the 
type specimens in the Shumard collection at the Washington University. 
We are under special obligations to Prof. Borden, of Borden Institute at 
New Providence, Indiana, for the opportunity of examining the original 
collection of Dr. Knapp, of Louisville, from the now exhausted Bear Grass 
locality near Louisville, containing some of the types of species described by 
Lyon, Shumard, and Yandell, which now form a part of the Museum of the 
Borden Institute. 
To Prof. S. Calvin we are indebted for the loan of fine specimens from 
the Hamilton of Iowa and New York, from which we made descriptions of 
several species. 
Our thanks are also due to Prof. W. H. Barris, of Davenport, Ia., who 
gave us the use of his type specimens and other valuable material from 
the Hamilton group of Iowa and Michigan, which were under his charge in 
the Museum of the Davenport Academy of Science. 
We also avail ourselves of this opportunity of expressing our high appre- 
ciation of the favors extended to us by Dr. G. Lindstrém, of the National 
Museum of Sweden at Stockholm, in which are deposited the magnificent 
collections of Crinoids from the Upper Silurian of Gotland that formed the 
basis of Angelin’s descriptions. Not only has he at all times allowed us the 
privilege of having special drawings made from unique specimens in 
the Museum, but on one occasion, on learning of the difficulty under which 
we labored from want of adequate material to study the genus Crotalocrinus, 
he sent us, without solicitation, a series of specimens, including some of 
Angelin’s originals, with liberty to retain them as long as might be necessary 
for the examination we desired to make. 
We have also to acknowledge our indebtedness to Mr. Walter R. Billings, 
of Ottawa, Canada, for the loan of types of Trenton species in his own col- 
lection, and also for his good offices in securing for our use the collections 
of Messrs. Stewart and I. F. Sowter. Besides this, Mr. Billings has from 
time to time furnished us valuable notes in relation to many rare and inter- 
esting forms, often illustrated by exquisite drawings from his own hand. 
We extend our thanks to Mr. John Stewart and Mr. I. F. Sowter, of Ottawa, 
Canada, for the use of their specimens, — Mr. Stewart having at one time 
sent us his whole collection for study. 
To the owners of private collections in the United States our obligations 
are so numerous and varied that we cannot attempt to express in proper 
terms of appreciation our indebtedness to each one. 
