274 PALEONTOLOGY OF ILLINOIS. 



below. Badials about twice as large as the smaller subradials, four 

 of them pentagonal and one on the right posterior side heptagonal, 

 counting three angles below. 



Brachials, five to the anterior ray, the first one of which is as 

 wide below as the first radial, but constricted above to correspond 

 w r ith the narrow, succeeding plates, which are quadrangular and 

 narrowly rounded on their external surfaces. The fifth brachial is 

 angular above, a little wider than those below, and gives support 

 on its upper sloping sides to the first divisions of the ray, which 

 thence continue simple to their extremities. 



The four other radials have each a single brachial, which is as 

 wide as the radial on which it rests, with a gaping suture between, 

 all pentangular, and supporting on their sloping upper angles the 

 first divisions of the rays. 



The left antero-lateral ray, after its first bifurcation on the bra- 

 chial plate, divides again on the sixth plate above, and the outer 

 division twice more on the seventh or eighth plate, while in the 

 right antero-lateral both divisions bifurcate on the sixth plate, and 

 the outer division again on the seventh or eighth plate, making five 

 divisions to this ray, which is probably the normal number in all 

 the rays except the anterior one, or twenty-two in the complete or- 

 ganism. The arms are composed of rounded, wedge-formed joints, 

 giving off strong pinnules alternately from their longest sides ; pin- 

 nules composed of rounded joints about twice as long as wide. 



Anal plates, five visible. The first one is pentagonal, and rests 

 between the upper angles of the two subradials and partly under the 

 lower angle of the right posterior radial. The second anal is larger 

 than the first, hexagonal, and rests upon one of the subradials, and 

 extends above the top of the left posterior radial. The third anal 

 is hexagonal, about as large as the first, on which it rests, and it 

 extends nearly half its length above the top of the posterior radial 

 on the right. The fourth and fifth anals are smaller, the one rest- 

 ing on top of the second anal and the other on the third. Column 

 unknown. 



Geological position and locality: Top of the geodiferous shales of 

 the Keokuk group, one mile below Keokuk, Iowa. 

 Nos. 184 and 243 of Mr. L. A. Cox's collection. 



I take pleasure in dedicating this beautiful species to my worthy 

 friend and co-laborer, Mr. Orestes St. John. 



