New Species of Crinoidea and oteer Fossils. 213 



on the fifth plate; above this the arms divide four or five times, 

 becoming very slender toward their extremities. 



The calyx plates are deeply impressed at their lateral margins, giv- 

 ing the strongly pentalobate character, The first radial plates have 

 also a strong elevated ridge passing across the lateral sutures from 

 plate to plate; this is nearly as high as the center of the plate. In 

 well-preserved specimens there is a small node at the lower lateral 

 angles of the first radial plates, and a corresponding node at the 

 upper extremity of the subradial plates. No other surface markings 

 have been observed. 



Column of medium strength, strongly pentangular or obsoletely 

 pentalobate, composed of alternating thick and thin plates of two or 

 more sizes ; the angles of the thick plates subnodose. At and near 

 the junction with the calyx, the column sometimes becomes deeply 

 pentalobate. 



This is a distinct and strongly marked species, and is readily dis- 

 tinguished from other forms by its deeply pentalobate calyx, and the 

 extremely rugose character of the arms, caused by the projection of 

 the upper margins of the short quadrangular plates. 



Formation and locality. In shales of the Hudson-river group, at 

 Cincinnati, Ohio. 



Hetekocrinus exilis n. sp. 

 Plate 5, fig. 16. 



Body small, with long slender arms ; calyx turbinate. 



Basal plates minute, appearing only as the upper joint of the 

 column. Subradial plates hexagonal ; height and width subequal. 

 Radial plates varying in number in the different rf},ys, and bifurca- 

 ting at difierent distances above their origin ; the postero-lateral rays 

 bifurcate on the second radial plates ; the antero-lateral rays bifurcate 

 on the fourth, and the anterior ray apparently on the sixth plate. 

 Anal plates not observed. 



Arms bifurcating once or twice ; plates of the arms long and slen- 

 der, the upper margins projecting, furnished with proportionally long 

 and slender ten taenia. 



Surface of plates smooth and having only the general curvature of 

 the body, except in the basal series, where each forms a small node 

 below the junction of the adjoining subradial plates. 



Column pentangular near its junction with the body, but more dis- 

 tinctly rounded below; composed of alternating thick and thin 

 joints. 



