316 PALEONTOLOGY OF ILLINOIS. 



AGASSIZOCRINUS HEMISPHERICUS, Worthen. 



PL XXIX, Fig. 7. 



Agassizocrinus hemisphericus, WOETHEN, Feb. 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 37. 



Body small, bowl-shaped, or hemispherical in outline, about once 

 and a half as wide as high to the summit of the radial series, rounded 

 at the base, and composed of massive, protuberant plates. 



Basals small, projecting but slightly below the subradials, forming 

 a little pentagonal star. No columnar facet is visible. 



Subradials a little longer than wide, strongly protuberant, three 

 of them pentagonal, and two on the posterior side hexagonal. 



Eadials pentagonal, three of them rather more than once and a 

 half as wide as long, the two on the posterior side rather narrower 

 than the others, and all truncated squarely across their summits for 

 the reception of the brachials. Sutures between all the plates of the 

 body distinct. 



Brachials as wide below as the radials, but strongly constricted 

 and sharply angular above, where they give support to the two di- 

 visions of the rays. The arm-plates attached are three in number, 

 the first nearly twice as long as the succeeding ones, and all quad- 

 rangular in form. 



Four anal plates are visible, the first is protuberant, pentangular, 

 about half as large as the largest radials, and rests squarely upon 

 the truncated upper margin of the right posterior subradial and under 

 the left side of the right posterior radial. The second anal is about 

 half as large as the first, longer than wide, and rests on the upper 

 margin of the left subradial. The other anals are smaller ; the third 

 rests between the first and second, and the fourth on the summit of 

 the second. Column unknown. 



Geological position and locality: Chester limestone, Randolph county, 

 Illinois. 



No. 2,451, Illinois State collection. 



