HEXACRINID^. 765 



the summit covered by a large, single oral plate, from tlie sides of which the 

 covering pieces pass out to the arms. Column large compared to the size of 

 the species; composed of high joints with serrated edges. 



Horizon and Locality. — Kinderhook group, Le Grand, Marshall Co., 

 Iowa. 



Tijjxs in the collection of Mr. Wm. F. E. Gurley, Danville, Ills. 



Dichocrinus laevis Hail. 

 Plate LXXVII. Figs. 7a, b, c. 



1859. Hall ; Suppl. Geol. Kep. Iowa, Vol. I., p. 83. 

 1881. W. and Sp. ; RcTision Palceocr., Part II., p. 8i. ' 



A beautiful little species. Calyx goblet-shaped, obcouical to the basi- 

 radial suture, not expanding above; the cross section slightly hexagonal. 

 Plates remarkably thin and flat, their surfaces thickly covered with small 

 granules. 



Basals forming a small obconical cup, which extends to about one third 

 the height of the calyx, and sometimes a little higher. Eadials nearly as 

 long as wide ; the sides parallel, except in the two posterior rays, where they 

 are wider above ; the lower faces moderately convex ; the upper almost 

 straight; facets small, occupying but one third the width of the plates; 

 their lower margins slightly thickened. Costals two, a little wider than 

 long ; the second sharply pentangular. Distichals almost as wide as the 

 costals, the line of union between the first and second less distinct than that 

 between the succeeding joints ; the second giving off either a very large 

 pinnule or an arm ; in the former case sometimes another bifurcation takes 

 place higher up. Arms uniserial, long, rather stout, very little tapering ; 

 composed of cuneate joints alternately arranged, which at the tips do not 

 touch the opposite side of the arm. Pinnules long, very stout, and not in 

 contact; the joints as wide as long. Interradials not visible from a side 

 viev,'. Anal plate a little higher than the radials, narrowest at the upper 

 end, and distinctly angular at the basi-radial suture. Anus placed near the 

 margin of the ventral disk, in the middle of a small protuberance. Column 

 round, small. 



Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 



The specimens figured are in the collection of Mr. F. M. Fultz, of Bur- 

 lington, Iowa. 



