New Species of Crinoidea and other Fossils. 209 



each bifurcation. The arm plates are smooth on the back ; the upper 

 lateral margins somewhat projecting for the attachment of the 

 tentacula. 



Column proportionally slender, obscurely pentangular, composed 

 of equal joints below, becoming more unequal near the junction with 

 the calyx. 



This species approaches more nearly to P. alternatus of the 

 Trenton limestone of ]N"ew York than to any other described form; 

 but it differs in having more elongate body plates ; the arm plates are 

 not compressed laterally, and the column is much smaller and com- 

 posed of equal joints, while in that species the joints are very unequal. 



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

 at Lebanon, Ohio. From Mr. J. Kelly O'^eall. 



POTERIOCKIX-IJS POSTICUS n. SJ>. / 



Plate 5, figs. 5, 6. 



Body small or of medium size, narrowly turbinate to near the 

 origin of the free arms. Basal plates small, a little wdder than high, 

 obtusely wedge-form on the upper end. Subradials, about twice the 

 size of the basals, somewhat regularly hexagonal, except the one on 

 the anal side, which is larger and heptagonal. First radials a little 

 wider than the subradials and not so high ; all the radial plates a 

 little wider than high. Anterior ray dividing on the seventh radial 

 plate, the other on the sixth radial ; divisions of the rays, above the 

 primary division, occurring at irregular distances, moderately diverg- 

 ing and rapidly decreasing in size ; the number of bifurcations can- 

 not be determined from the specimen under examination. Arm 

 plates, as far as seen, rather shorter than wide, equal sided. 



Anal area large ; first anal plate largest, pentangular or hepta- 

 gonal, resting upon the larger subradial, and supporting two or three 

 plates on its upper edges, above which rises the strong, broad pro- 

 boscis, which is composed of eight ranges of hexagonal plates, 

 decreasing in size regularly from below upwards, and marked by ele- 

 vated ridges passing to those of the adjacent ranges. 



Surface of plates smooth. 



The most conspicuous feature in this species is the broad anal area 

 surmounting the large subradial plate. 



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

 \ Cincinnati, Ohio. From Mr. C. B. Dyer. 



14 



