12 



rOTEKIOCRINUS BRI^.RIUS. N. SP. 



Body of medium size, cup shaped, base depressed ; the basal plates 

 small, not extending beyond the columnar facet. Subradials promi- 

 nent in the center and depressed at the angles, three hexagonal and 

 two on the posterior side rather larger than the others, and hep- 

 tagonal. 



Eadials pentagonal, nearly twice as wide as long, depressed on 

 their lower margins to correspond with the depressions in the sub- 

 radial plates. They are constricted across the middle, and project- 

 ing on their upper margins, with a distinct suture between them 

 and the brachial plates. 



First brachial quadrangular, the second pentangular, sharply an- 

 gular above, giving support on its upper sloping angles to the first 

 divisions of the rays. 



The arms on the three anterior rays, after their first division on 

 the second radials, divide at least four times, and one of them, the 

 left antero-lateral ray five times, the division in every case taking 

 place on the outer branch, as in Zcacrinus, while the inner branches 

 continue single to their extremities. The divisions generally occur 

 on the sixth, eighth, twelfth or sixteenth plate, making ten arms to 

 two of these rays, which is probably the normal number, and eleven 

 to the other. On the posterior rays, these divisions take place on 

 the fourth, sixth and eighth plates. This gives an arm formula of 

 fifty arms, as the normal number for this species. 



First anal plate hexagonal, about as large as the smallest sub- 

 radials, second and third rather smaller than the first, and pll ar- 

 ranged as usual in this genus. They are all depressed at the angles, 

 though not quite so much as the other plates of the body. Column 

 unknown. 



Position and locality : Upper part of the geodiferous shales of the 

 Keokuk group, one mile below Keokuk. 



Nos. 100 and 185 of Mr. L. A. Cox's collection. 



POTERIOCRINUS ASPERATUS. N. SP. 



Body depressed, forming a low saucer-like cup below the summit 

 of the radial plates. Base depressed, and basal plates concealed by 

 the upper columnar joints. Subradials small, their lower angles 

 concealed in the basal concavity. 



liadials about twice as wide as long, pentagonal, without any well 

 defined suture between them and the first brachial plates. 



Brachials two, about the same size as the radials, the first quad- 

 rangular, and the second pentangular, giving support above to tlie 

 first divisions of the rays. 



Arms composed of rounded, nearly quadrangular joints, and after 

 the first division on the second brachial they divide twice more in 

 the posterior rays, first on the seventh, and each division again on 



