10 



Position and locality: Upper part of the Keokuk limestone, 

 Hamilton, Illinois. 

 No. 269 of Mr. L. A. Cox's collection. 



POTERIOCKINUS TENUIDACTYLUS. N. SP. 



Body of medium size, depressed cup-shaped, more than twice as 

 wide as high, Base depressed, basal plates small and concealed in 

 the basal cavity. Subradials as long or longer than wide, three 

 hexagonal and two on the anal side heptagonal. 



Radials about twice as wide as long ; heptagonal, and truncated 

 squarely across their upper margins for the reception of the brachial 

 series. 



Brachials two, the first quadrangular, and the second pentangu- 

 lar, both as wide or a little wider than the radials ; the second sup- 

 porting on its upper angles the first divisions of the arms. The 

 arms are composed of wide, short, quadrangular joints, and bifur- 

 cate the second time on the fourth and sixth plates above the brach- 

 ials, beyond which they are all simple to their extremities, making 

 four arms to each ray. Above the second bifurcation the plates of 

 the arms gradually diminish in width, and become slightly wedge- 

 formed, giving off strong pinnules from their longest sides. 



Anal area proportionately large, with nine small anal plates visi- 

 ble. The first is pentagonal, and rests between two of the sub- 

 radials and partly under one side of the right posterior radial. The 

 two succeeding anals are larger, placed side by side, their lower mar- 

 gins resting, the left one on the truncated margin of one of the 

 subradials. and the other between the upper angle of the first anal 

 and the left margin of the first radial to the right. The next series 

 of anals consists of three smaller plates placed side by side, and 

 these are succeeded by three more that are not fully exposed. 



Column unknown. 



Position and locality : Upper shales of the geode bed. one mile 

 below Keokuk, Iowa. 



No. 403 of Mr. L. A. Cox's collection. 



POTERIOCRINUS OCCIDENTALIS. N. SP. 



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. 



Eadials 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, 



