BATOCRINID^. 497 



five smaller plates, which are succeeded by numerous others. Ventral disk 

 low hemispherical; the plates perfectly flat, except the first radial dome 

 plates, which are slightly nodose, very large, and placed near the arm bases. 

 Orals in contact laterally ; the posterior one central, twice as large as the 

 others, and interposed between them. Interambulacral plates very numer- 

 ous, and forming a continuous ring around the orals, covering completely 

 the disk ambulacra ; those of the anal side are somewhat smaller, and as 

 numerous as all other interambulacral plates together. There being no 

 anal ridge, the plates of the posterior area grow smaller as they approach 

 the anus, which is excentric and directed obliquely upwards. 



Horizon and Locality. — Keokuk group; Green Co., Ills., and Keokuk, 

 Iowa. 



Type in the (Worthen) Illinois State collection, Springfield. 



Remarks. — This species differs from all others of the same horizon in 

 the peculiar structure of the disk. It is or\\j found in the shaly layers, 

 which constitute the middle part of the Keokuk group, and good specimens 

 are extremely rare. 



Agaricocrinus nodulosus Worthed. 

 Plate XL. Fig. B, and Plate XLIIL Figs. 7a, h. 



1891. Geol. Eep. Illinois, Yol. Tin., p. 9i, Plate 13, Eigs. 1, la. 



Calyx broadly pyramidal with slightly concave sides. Its lower face 

 deeply excavated to the middle of the first distichals, forming a rounded, 

 inverted cup, of which the posterior side is deeply notched, while the margin 

 toward the other sides inclines but very little. The calyx, when placed upon 

 its dorsal side, rests upon the distichals, and while the interbrachial plates of 

 the four regular sides almost touch the bottom, those of the anal side are 

 more remote, leaving, when viewed from the side, a large, triangular vacant 

 space. The plates occupying the basal concavity, comprising the basals, 

 radials and costals, are perfectly flat ; the distichals and palmars, however, 

 which form its surrounding margin, are more or less convex, and the bases 

 of the arms almost touch the bottom of the calyx. 



Basals rarely visible beyond the column. Eadials somewhat irregular in 

 size, the posterior ones generally longer than the others. First costals 

 quadrangular, once and a half as wide as long, their lateral faces convex; the 

 second as large as the radials and pentangular. Distichals quite variable in 

 form and size, as well as in number among the rays. In the anterior ray. 



