INVEETEBEATES. 285 



differs from that in its more elongate body, the very thin plates of 

 which it is composed, as well as in the number and mode of bifur- 

 cation of the arms. 



Position and locality : Keokuk limestone, Keokuk, Iowa. 



Collection of the author. 



POTERIOCKINTJS ElCHFIELDENSIS, Worthen. 



PI. XXX, Fig. 5. 



Pjteriocrinus Richfieldensis. WOKTHEN, Feb., 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 15. 



Body small, turbinate, length and breadth about equal. Basals 

 moderately large in proportion to the entire body, projecting above 

 the columnar facet so as to form a shallow pentagonal cup. 



Subradials larger than the basals, the two on the posterior side 

 the longest, and hexagonal. 



Eadials wider than long, pentagonal, with a well denned and 

 rather gaping suture between them and the succeeding brachials. 

 In the right posterior ray the brachial is twice as long as wide, 

 pentagonal, supporting on its upper sloping sides the first divisions 

 of the ray. In the left posterior ray the brachial is divided, mak- 

 ing two brachials in this ray, the first quadrangular, and the second 

 short and pentangular, but I am inclined to regard this as acci- 

 dental, and to believe that one brachial to each ray is the normal 

 number. 



The first anal plate is a little longer than wide, hexagonal, and 

 rests between the sloping sides of the two posterior subradials, and 

 partly under the left side of the right posterior radial. The second 

 anal is a little larger than the first, and rests on the upper margin 

 of the left posterior subradial. The third annal is smaller than the 

 others, and rests upon the first. 



Arms composed of rounded joints, not wedge-shaped, and divide 

 the second time on the eighth plate above the brachials, beyond 

 which they are simple in the posterior rays, the only ones visible 

 in our specimen. 



Column round, composed of short joints, and rather thicker at 

 the base of the calyx than below. 



Position and locality.- Shaly sandstones of the Kinderhook group, 

 near Eichfield, Ohio. 



No. 2,474, Illinois State collection. 



