4 SMITHSONIAN INSTITUTION 



Abundant evidence of his care and skill will be found in the plates accompany- 

 ing this volume, in which every one of Angelin's types belonging to this group 

 has been refigured and his erroneous illustrations corrected, while many new 

 and important figures have been added. I wish to record my extraordinary 

 obligations to Mr. Liljevall for a piece of accurate and truly scientific work 

 such as I think has never been done before under like circumstances. Supple- 

 menting the Stockholm material, I was able by purchase and by the employ- 

 ment of collectors on the island to accumulate a very fine series of the Gotland 

 crinoids, including a number of extremely important specimens belonging to 

 this group. The study of all this material has resulted in clearing up several 

 perplexing points left obscure by Angelin. 



In America all the collections of museums and individuals have been 

 placed without reserve at my disposal, with liberty to remove such of the 

 material as I desired to my own quarters for study at leisure. It is impossible 

 to express the full measure of my appreciation of this generous assistance, or 

 the sense of obligation which I feel, not only for the facilities thus extended to 

 me, but still more for the extraordinary courtesy and good-will with which they 

 were offered. A brief enumeration of these collections follows : 



The facilities of the United States National Museum have at all times 

 been freely accorded in aid of my studies upon the crinoids, especially under 

 the administration of the Hon. Charles D. Walcott, Secretary of the Smith- 

 sonian Institution, and of Dr. Richard Rathbun, Assistant Secretary in charge 

 of the National Museum. In 1909, upon being informed of my desire to 

 arrange for a permanent resting place for my collection of fossil echinoderms 

 and library pertaining thereto, which had by that time grown beyond the 

 capacity of the private museum formerly maintained at Burlington, Iowa, 

 Dr. Walcott offered to provide suitable quarters for the collection, as well as 

 for my researches, in the magnificent new building of the National Museum 

 then under construction. Accordingly, in 191 1, the transfer was made; a selec- 

 tion of the specimens especially adapted for exhibition was installed in the Hall 

 of Invertebrate Paleontology; the remainder, contained in about one thousand 

 of the usual museum trays, was deposited in the research rooms assigned to me, 

 where for the first time in many years the whole of it became conveniently 

 accessible for study. In these commodious quarters the prosecution of my 

 researches has been facilitated and made pleasant by the unvarying kindness 

 of Dr. George P. Merrill, Curator of the Division of Geology, and Dr. R. S. 

 Bassler, Curator of Paleontology. To Dr. Bassler I am especially indebted, 

 along with many other favors, for valuable assistance to my collectors in the 

 field in the interpretation of the stratigraphy, and for the use of his fine photo- 

 graphic equipment which has been at all times at my disposal, together with 



