278 PALEONTOLOGY OF ILLINOIS. 



POTERIOCRINUS occiDENTALis, Worthen. 



PI. XXVII. Fig. 2. 



Poleriocrinus, occidentalis, WOKTHEN, February, 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, page 10. 



Body cup-shaped, about twice as wide as high. Base depressed, 

 the basals small and hidden under the first columnar joints. Sub- 

 radials hexagonal and heptagonal, the lower angle curving under to 

 form a part of the basal concavity. 



Radials pentangular, nearly twice as wide as long, with a gaping 

 suture between them and the brachials. 



Brachials on four of the rays pentangular, widest below, slightly 

 constricted in the middle, and angular above, supporting on their 

 sloping sides the first division of the rays. Another bifurcation 

 takes place on the tenth plate above the brachials in these four rays, 

 beyond which they are simple to their extremities. The anterior 

 brachial is quadrangular, constricted above, and supports a single 

 arm, making 17 arms altogether for this species. 



The anal side of the specimen is distorted so that the number and 

 form of the anal plates cannot be clearly determined ; but three can 

 be seen ; the second one much larger than the others, and apparently 

 arranged as usual in this genus. 



Column moderately stout, round and composed at the summit of 

 evenly- sized plates, that alternate with thinner ones below. 



This species is nearly related to Pot. (Scaph.) unions, of Hall, but 

 differs essentially from that in the number and bifurcation of the 

 arms. 



Position and locality: Upper beds of the Keokuk limestone, Ham- 

 ilton, Illinois. 



No. 170 of Mr. L. A. Cox's collection. 



POTEBIOCRINUS ASPER, Worthen. 



PL XXVII, Fig. 8. 



Poteriocrinus asper, WOKTHEN, February, 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 11. 



Body of medium size, basin-shaped, base slightly depressed, the 

 basal plates being concealed by the columnar joints. Subradials 

 prominent, length and breadth about equal, the lower angles forming 



