29 



gaping suture. The second radials or first arm plates appear 

 to be attached to the vault but they are followed by two rounded 

 plates and these by an axillary plate. If these four plates 

 are attached to the vault and the arms do not become free 

 until they bifurcate, then this is a very remarkable species. 

 The five radial series bifurcate on the fourth plate above the 

 gaping suture and it is very clear that the arms are then free. 

 Above this part our specimen does not preserve any char- 

 acters. 



The azygous area is also peculiar. The first plate is large 

 and protuberant. It truncates a subradial broadly and slightly 

 truncates another and reaches higher than the adjacent first 

 radials, where it has two superior sloping sides and supports 

 on each a series of rounded plates, that look externally like 

 arm plates but of course they form part of the vault. 



This species is distinguished by its form, radial system, and 

 hexagonal first azygous plate. The calyx is like that of a 

 Poteriocrinus and the pits and azygous area and plates link it 

 with Barycrinus. It can not be mistaken for any other species 



Pound in the Keokuk Group, at Crawfordsville, Indiana, and 

 now in the collection of Wm. F. E. Gurley. 



POTERIOCRINUS ALBERSI, n. Sp. 



Plate II, Fig. 15, azygous side magnified two diameters; Fig. 16, 

 opposite view, two diameters; Fig. 17, basal view. The 

 specimen is slightly compressed. 



Species small; plates covex, angular, rough. Calyx saucer- 

 shaped, about two and a half times as wide as high; plates 

 convex, surface granular. 



Basals hidden, or nearly so, by the column. Subradials as 

 long as wide and form with the basals a low cup. First radials 

 one-half wider than long, pentagonal, highly convex toward 

 the superior central part, truncated the entire width above and 

 separated from the second radials by a gaping suture. Second 

 rsd.ials about as long as wide, constricted and angular in the 

 middle, axillary and support upon the upper sloping sides the 

 free arms. The arms do not bifurcate. There are, therefore, 

 ten arms in this species. The arms are long and composed of 



