14 



pentagonal, wider than long. First brachial quadrangular, second 

 brachial pentagonal, and both as wide or a little wider than the 

 radials below. 



The arms of only one of the rays, the left antero-lateral, is pr e- 

 served so that its structure can be made out. This ray divides on 

 the second brachial, and the left branch twice more on the sixth and 

 eighth plate above, while the right branch divides at least four times 

 on the sixth and eighth plates, making at least eight arms to this 

 ray. Anal series cannot be seen clearly enough to be fully deter- 

 mined, they are apparently arranged as usual in this genus. 



Column round, and composed of thin, vmequal joints. 



This species is evidently nearly related to Hall's Pot. (Scaph) 

 (cquaUs, but differs from that in the relative size of its subradial 

 plates, and in the number and mode of bifurcation of the arms. 



Position and locality : Keokuk limestone, Nauvoo, 111. 



Illinois State collection. 



POTEKIOCRINUS OTTERENSIS. N. SP. 



Body above the medium size, basin-shaped, about once and a half 

 as wide as high, base depressed and the basal plates hidden by tne 

 column, which is quite stout and pentalobate where it joins the body. 



Subradials about one-fourth wider than long, the lower angle 

 curving inward to form apart of the basal concavity. The center of 

 these plates is smooth and a little protuberant, with four deep in- 

 dentations on their borders, two of which are lateral, to meet those 

 of the adjacent subradials, and two directed obliquely upward to 

 meet similar depressions in the radial plates. 



Radials wider than long, constricted across the middle, and pro- 

 jecting on their upper margins, with two slightly oblique depressions 

 below, that meet two of those in the subradial plates. They are 

 pentagonal in form and support on their upper truncated margins 

 the brachial series. 



Brachials one to each of the postero-lateral rays, smaller than 

 the radials, slightly constricted, and sharply angular above, giving 

 support to the first divisions of the rays. Arm structure unknown. 



Three anal plates are visible, the first nearly as large as the sub- 

 radials, the others a little smaller, and all having from four to six 

 depressions around their borders that correspond to similar depres- 

 sions on adjacent plates. The anal plates have been shoved out of 

 their true position by the crushing of the specimen, so that their re- 

 lation to the adjacent plates cannot be clearly determined. 



Position and locality : This unique form was obtained from the 

 Keokuk limestone, on Otter Creek, Jersey county, 111. 



Illinois State collection. 



POTEKIOCRINUS SUBRAMULOSUS. N. SP. 



J^ody turbinate or obconical, higher than wide to the top of the 

 radial series, and composed of very thin, smooth plates. Basals 



