18 



appear to be simple, which would give four arms to this ray. If the 

 posterior rays, which are concealed iu the rock in our specimen, cor- 

 respond with the antero-lateral ray, it would give eighteen arms to 

 the entire animal. Anal area and column unknown. 



I take pleasure in dedicating this species to my esteemed friend, 

 Henry Talbot, Esq., of Waterloo, to whom I am indebted for many 

 acts of personal kindness, and for some interesting fossils. 



Position and locality : St. Louis limestone, Monroe county, 111. 



Illinois State collection. 



POTERIOCRINUS VALIDUS. N. SP. 



Body more than twice as wide as high, forming a low shallow 

 cup. Basals small and concealed by the first columnar joints. 

 Subradials hexagonal on the anterior side, strongly protuberant in 

 the middle and depressed at the angles, giving a very rugged appear- 

 ance to the outer surface of the body. Radials pentagonal, about 

 twice as wide as long, depressed at their lower angles to correspond 

 with the depressions of the subradial plates. 



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

 lar, supporting on their upper sloping sides the first divisions of the 

 rays. All the plates to the top of the second brachials, possess the 

 rugged character mentioned above. Anal series unknown. Arms 

 not preserved on the anterior ray, but from the partial preservation 

 of those on the posterior side, there seem to be not more than two to 

 each ray. Column round and rather delicate, composed near the 

 body of joints of unequal size. 



Position and locality : Warsaw beds of the St. Louis group, 

 Warsaw, 111. 



Illinois State collection. 



POTERIOCRINUS CLAYTONENSIS. N. SP. 



Body of medium size, basin shaped, about once and a half as wide 

 as high to the top of the radial series. 



Basals small and entirely concealed in the basal concavity by the 

 first columnar joints. Subradials nearly or quite as long as wide, 

 their lower angles curving into the basal concavity. 



Radials once and a half as Avide as long pentagonal, and truncated 

 squarely across the upper margins for the reception of the brachial 

 series. 



Brachials on three of the rays about the same size and form_ as 

 the radials, and give support on their upper sloping sides to the first 

 divisions of the rays. 



The arrangement and number of the arms cannot be determined 

 from the specimen in hand, but in the right antero-lateral ray a 

 bifurcation takes place on the sixth plate above the brachial, beyond 

 which the divisions are unknown. The arms are composed of wide 

 short quadrangular plates, as in Zcacrhuis, and wonhl be closely 

 joined when folded as in that genus. Three anal plates are pre- 



