FOSSILS OF THE NIAGARA GROUP. 367 



curve of the base to nearly one-third the height of the cup. The 

 subradial plates form nearly one-half the height. The column is 

 large and round. Arms unknown. The surface of the plates in 

 the casts is marked by strong radiating striae. 



Formation and Locality. — ^In limestone of the age of the Niagara group at 

 Racine, Wisconsin. 



Ctathocrinus waukoma, n. s. 



PLATE XI, FIGS. 11, 12. 



Calyx rotund below, subhemispheric ; the sides above the middle of the 

 subradial plates nearly straight or but little spreading. Basal plates 

 small ; subradial plates large, curving upward for about half their 

 length ; radial plates about as large as the subradial. The subradial 

 plates have been marked by a central node, fi-om which radiate 

 strong ridges to the margins, joining similar ridges on the adjacent 

 plates. Two of these from the lower sides of each of the radial 

 plates converging to near the centre of that plate, and uniting, extend 

 in a single ridge to the upper margin. The surface markings beyond 

 the strong ridges are unknown. 



This species is of different form, with more elevated sides and different 

 surface markings from C. fusilliis^ which occurs in the same formation. 



Formation and Locality. — In limestone of the Niagara group at Racine 

 and Waukesha, Wisconsin. 



GENUS ICHTHYOCRINUS, Conrad. 



ICHTHYOCRINUS SUBANGDLARIS , HaLL. 



PLATE XI, FIGS. 15, 16. 



Icthyocrinus subangularis, Hall; in Trans, of the Albany Institute, IV, p. 201. 1862. 

 Ichthyocrinus corbis, W. & M.; in Mem. Bos. Soc. Nat. Hist., I, p. 89. 1865. 



This species is more narrowly turbinate than the /. laevis of the 

 Niagara group in New York, and has the calyx distinctly angular. 



The original of the species occurs at Waldron, associated with well 

 marked Niagara forms ; and a specimen of the same species has been 

 found at Bridgeport, Illinois, in limestone of the age of the Niagara group. 



Possibly a larger collection of specimens may show gradations from the 

 rounded and broadly turbinate typical species of the genus, to the nar- 

 row and subangular forms of Indiana and Illinois; but we have no 

 intermediate forms at the present time. 



