556 PALEONTOLOGY OF ILLINOIS. 



wide as high ; facet for the attachment of the column about 

 one- third as wide as the base, with a small marginal rim. 

 Pirst radial plates nearly oblong, being longer than wide, 

 with sub-parallel sides; some of them with two obscure 

 linear ridges extending from the middle to the upper side, 

 and slightly diverging to the base; each moderately concave 

 above for the reception of the next range of pieces. Second 

 radial very minute, about twice as wide as long, but not 

 equaling the breadth of the slight concavity in the upper 

 side of the first radials. Third radial pieces slightly wider 

 than the second, and about of the same length, pentagonal, 

 and each supporting an arm on each superior sloping side. 

 Arms each divided on the second piece, beyond which they 

 are simple, at least for four or five pieces above, and com- 

 posed of a single series of quadrangular pieces, about as 

 long as wide, excepting the first, which is near twice as 

 long as wide. Tentacles apparently comparatively stout. 

 Column near the base nearly or quite round, and composed 

 of very thin pieces. Surface smooth. 



Length of body to summit of first radial pieces, 0.12 

 inch; breadth of do., 0.12 inch; length of arms, about 0.30 

 inch; thickness of column, 0.02 inch. 



This very small species differs remarkably from all tlie others with 

 which we are acquainted, resembling it in other respects, not only in its 

 small size, but in having two minute radial pieces in each ray, above 

 the larger first radials composing the body, thus making three radials 

 to each ray. 



Locality and position Pope county, Illinois ; Chester division of the 

 Lower Carboniferous series. 



GENUS AGASSIZOCRINUS. 

 AGASSIZOCEINUS PENTAGONUS, Worthen Ms. 



PL 21, Fig. 10. 



BODY, viewed from below, pentagonal in outline, base 

 rather large, suture lines distinct, point of attachment for 



