244 PALAEONTOLOGY OF ILLINOIS. 



of being connected by many interradials, as in tbe otber species, while their 

 arms, which are proportionally small, are clustered together in little bunches 

 at the extremities of the rays, far out from the body. 



These last mentioned species, with their long spreading and bifurcating rays, 

 bearing their numerous clusters of little, curled-up arms at their extremities, 

 must have presented much the appearance of dried examples of the existing genus 

 Astrophyton, though we cannot agree with Messrs. Lyon and Casseday, in the 

 opinion that they form a connecting link between the Crinoulea and Asteroidea, 

 or are more nearly allied to the star fishes than other palaeozoic crinoids, their 

 resemblance being merely simulative, and not due to any close analogy of struc- 

 ture. 



The species of this group yet known to us, are confined to the Subcarbonif- 

 erous rocks, and seem to be peculiar to America. 



Onychockinus monkoensis, M. and W. 



PL 17, Fig. 1. 



I 



Forbesiocrinus rnonroensis, Meek and Worthen, June, 1861. Proceed. Acad. Nat. Sci., 

 Philad., p. 130. 



Body below the free arms apparently depressed basin-shaped, 

 composed of nearly smooth rather thick plates, connected by 

 linear sutures. Base small, and nearly hidden by the column. 

 Subradial plates of moderate size, four of them pentagonal, 

 and one on the anal side hexagonal, with unequal sides — its 

 upper side being short, and distinctly sinuous in the middle, 

 for the reception of the small first anal piece. First radials 

 about twice as wide as high, hexagonal in form, and nearly 

 twice as large as the subradials. Second, third and fourth 

 radials in two of the rays (and one or two more in another), 

 all nearly of the same length, hexagonal in form (excepting 

 those on the two posterior rays, which have their ends next 

 the anal space truncated so as to become pentagonal), and all 

 nearly twice as wide as long. Last primary radial pieces 

 smaller than the others, pentagonal, and supporting on their 

 superior sloping sides the abruptly diverging first divisions, 

 each of which latter gives put several branches above. 



