202 



PALEONTOLOGY OF ILLINOIS. 



,-,. , , costate.* Another difference of still 



rig. 11. 



greater importance is, that in the species 

 now under consideration the third radial 

 pieces project so strongly outwards, and 

 the anal and interradial spaces are so 

 deeply sinuous, that these pieces (as seen 

 from below) appear connected with the 

 body by the inner margin only; while in 

 authentic specimens of A. stellaris, from 

 Belgium, now before us, they are so 

 deeply implanted between the second 

 range of interradials, as to be scarcely 

 visible from below. Again, in A. stel- 

 laris, there is but one secondary radial 

 between the first and second bifurcations 

 of each ray, while in the American spe- 

 cies there are two. 



Locality and position: Cedar creek, Warren county, Illinois; Burlington 

 limestone, of the Subcarboniferous series. 



Actinocrinus concinnus — (Near nat. size). 



Actinocrinus scitulus, M. and W. 



PI. 15, Fig. la and lb. 



Actinocrinus scitulus, Meek and Worthen, Sept., 1860. Proceedings Acad. Nat. Sci., 



Philad., p. 386. 

 A. rusticus, Hall, Feb., 1861. Descrip. Crinoidea (Prelim, notice), p. 2; Boston 



Jour. Nat. Hist., vol. vii, p. 267. 

 Compare A. Sillimani, M. and W., June, 1861. Proc. Acad. Nat. Sci., Philad., p. 134. 



Body rather under medium size, more or less nearly urn- 

 shaped, the summit being depressed-convex, and the calyx 

 below the arms abconical, with a truncated, slightly expanded 

 base; sides expanding regularly from the base to the third 

 radials, above which the secondary radial and first brachial 

 pieces extend out horizontally, leaving excavated anal and 

 interradial spaces between the clusters of arms. Base of mod- 



* We should remark here, that the Belgian specimens of A. stellaris, with which we 

 are making the comparison, are more strongly ribbed than those figured by de Koninck 

 and Lehon, and far more nearly like the American form under consideration. 



