ARTICLE I. 



Descriptions of fifty-four new species of crinoids from the lower 

 carboniferous limestones and coal measures of illinois and 

 IOWA. By a. H. Worthen, 



State Geologist. 



For the use of a part of the crinoids described in the following 

 pages, I am indebted to the liberality of Mr. L. A. Cox, of Keokuk, 

 Iowa, who, by his zeal and indefatigable industry as a collector, has 

 brought together one of the finest collections of these beautiful fos- 

 sils ever obtained from the Keokuk limestone, and he has also been 

 so fortunate as to obtain a large number of specimens from a higher 

 horizon in the Keokuk group, than that from which most of the 

 crinoids peculiar to this formation had previously been obtained. 



In the winter of 1879, a few finely preserved crinoids were found 

 by Mr, Cox and Mr. Anderson, of Keokuk, in loose pieces of sandy 

 shale at the foot of the bluff about a mile below the city, which had 

 evidently fallen down from above, and an ineffectual attempt was at 

 once made to discover the exact horizon from which the shaly frag- 

 ments had come. On a subsequent visit by Mr. and Mrs. Cox to 

 the locality, the latter, who is also an excellent collector, succeeded 

 in locating the exact spot from which the crinoids had come, and 

 in finding the fossils in situ. 



By quarrying into the bluff at the right point, some four or five 

 hundred specimens have been obtained by different collectors who 

 have visited the locality, all secured from a surface scarcely more 

 than six feet square, and from a stratum, only a few inches in thick- 

 ness, situated near the dividing line between the geodiferous shales 

 of the Keokuk group, and the overlying Warsaw beds. 



In 1880 another discovery of fossil crinoids was made by Mr. N. 

 K. Burket, of Keokuk, in the Keokuk limestone at Hamilton, Illi- 

 nois. This was in a different geological level from that just de- 

 scribed, and it has not afforded as large a number of specimens as 

 the other, but many of them are remarkable for their large size and 

 fine state of preservation. Moreover, they are generally specifically 

 distinct from those obtained in the sandy shale, and many of the 

 species found here are common in the Keokuk limestone at other 

 localities. Mr. Burket and Mr. Cox worked this locality jointly, and 

 in a surface of about 8 to 10 feet square they obtained from 175 to 

 200 crinoids, many of them with the arms attached. They were all 

 obtained from a cherty layer some three or four inches in thickness, 

 intercalated in the upper part of the Keokuk quarry-rock, some five 

 or six feet below the base of the geodiferous shales, and some forty 

 feet below the sandy shales that were so prolific in similar forms on 

 the Iowa side of the river. 



