258 Cincinnati Socictij of Natural History. 



The summit is marked by a central ambulacral opening, an anal 

 opening or moutli close to the margin, and ten marginal supports of 

 the interambulacral areas, one being placed upon each side of the am- 

 bulacral spaces. 



This species is founded upon an exceedingly perfect and unique 

 cast now in ni}' own collection, but which was found by W". C. Egan? 

 of Chicago, Illinois, in the Cherty beds of the Keokuk Group, at New 

 Bloomfield, Missouri. It is the first species described in America, 

 from rocks of the age of the Keokuk Group. 



Strotocrinus bloomfieldensis, n. sp. 



Plate XV., fig. 6, natural size ; 6a, view of the summit of a cast. 



Body, large, urn-shaped below, and widely spreading at the arms 

 above. Basal plates, wider than long, and about two thirds the size 

 of the first radials. 



First radial plates large, higher than wide, three of them hexag- 

 onal, and two of them heptagonal. Second radials, not more than half 

 the size of the first, hexagonal, and about as wide as high. Third 

 radials, heptagonal, about as wide as high, a little smaller than the 

 second radials, and supporting upon their superior sloping sides the 

 secondary radials, from the summit of which spring the plates that 

 form the lower part of the spreading canopy, which is not preserved in 

 our specimens. 



The first interradial plate is almost regularl}' hexagonal, and of the 

 same size as the second radial. It supports upon its superior sloping 

 sides two second interradials, which are a little smaller than the third 

 radials; one of them is pentagonal, and the other hexagonal. These 

 are followed by two third-interradials, which are arranged between the 

 third radials; and these in turn b}' two fourth interradials, arranged 

 between the secondary radials. 



The first azygos plate is heptagonal, resting upon two basal plates, 

 and between two first radials, and surmounted by three plates, it is 

 not to be distinguished in a basal view from the first radials. It is, 

 however, a little smaller than the first radials. Above these, on the 

 azygos side, the outlines of the plates are not preserved in our speci- 

 mens. 



The numbei- of arms can not well be determined, but as there are 

 ten secondary radials, and the cast of the openings connecting with 

 the arm furrows, bifurcate within the length of a small plate from these 

 secondai'ies, and again and again bifurcate, so that in our illustrated 

 fragmentary specimen, we have five of these branches from a single 



