INTRODUCTORY REMARKS. 



For the use of several of the crinoids described and figured in 

 this volume, I am indebted to the liberality of Mr. L. A. Cox, of 

 Keokuk, Iowa, who, by his zeal and indefatigable industry as a col- 

 lector, has brought together one of the finest collections of these 

 beautiful fossils ever obtained from the Keokuk limestone, and a 

 part of them were found in a higher position in the Keokuk group 

 than that from which this class of fossils has usually been obtained. 

 These came from a sandy stratum only a few inches in thickness, 

 situated near the dividing line between the geodiferous shales of 

 the Keokuk group and the overlying Warsaw beds, which form the 

 upper part of the river bluff about a mile below the steamboat land- 

 ing, where the fossils were obtained. 



Another very interesting and productive locality was found by Mr. 

 N. K. Burket, of Keokuk, in the Keokuk limestone at Hamilton, 

 Illinois, and from this a part of the following species were obtained. 

 These came from a cherty layer some three or four inches in thick- 

 ness, intercalated near the top of the quarry rock at Hamilton, some 

 five or six feet below the base of the geodiferous shales. These two 

 very limited horizons have furnished all the Keokuk species, with 

 one or two exceptions, that are described and illustrated in the fol- 

 lowing pages. 



The species from the St. Louis and Chester groups were all col- 

 lected by the author, and form a part of the Illinois State 

 Collection. A. H. W. 



