INVERTEBRATES. <r> 



I>asals and first radials smooth, second radials and succeed- 

 ing arm plates slightly nodose. 



The anterior and left anterior rays have three arms each, and 

 the right anterior and the two posterior rays four each, making 

 altogether eighteen arms, which is probably the normal number. 



Immediately above the arm openings there are from three to 

 four rather large nodose plates, while those forming the upper 

 part of the dome are smooth or but slightly elevated in the 

 center. 



Anal area large, protuberant, and composed of twenty-four 

 or more nearly smooth plates, above which the anal opening is 

 situated. 



The basal and radial plates are obscured by cherty material, 

 so that their relative size and form cannot be determined. 



\Ve dedicate this fine species to the Hon. Wm. McAdams, of 

 Alton, by whom it was found. 



Position and locality: Keokuk limestone, Jersey county, Illi- 

 nois. 



Collection of A. H. Wortheu. 



GENUS CENTROCRINUS. Wachsm. and Spr. 



CKNTKOCKLXUS TEXNESSEEXSIS. (sp. nov.) 



PI. XIV, Fig. 1. 



Calyx broadly turbinate, breadth at the base of the arms 

 equal to once and a half its height. 



The basal plates form a low pentagonal cup, about twice as 

 wide as high, with projecting lower borders, which form a rim 

 around the columnar facet. 



The first radial plate is as large or larger than the second 

 and third combined, and has seven distinct angles. 



Second radials quadrangular, about twice as wide as long; 

 third radials about the same size as the second, axillary, and 

 supporting the succeeding radial series, which in rays visible on 

 our specimen consists of a single axillary plate, giving four 

 arms to each ray. 



One long oval plate fills each of the interradial spaces on the 

 free side of the specimen in hand. 



The arms are not preserved beyond the fifth or sixth joint, 

 and the fifth plate on one arm seems to be an axillary plate. 



