Carboniferous Rocks of the Mississippi Valley. 285 



its high dome and strongly inflated anal side, which has 

 the appearance of a tumor. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collection of C. A. Wliite. 



GENUS PLATYCRINUS, Miller. 



Platycrinus eleg-ans (n. s.). Body small, narrowly sub- 

 turbinate. Basal plates a little constricted near the mid- 

 dle, the lower sides slightly projecting ; the small plate is 

 nearly twice as long as its greatest width. Radial plates 

 long and narrow, quadrangular, very gradually increasing 

 in width upwards, once and a half as long as wide. The 

 articulating scar for the attachment of the arms small, lit- 

 tle more than one third the width of the plate, and scarcely 

 extending below the top. Arms bifurcating on the second 

 plate above the first radial, and each branch again divid- 

 ing on the third or fourth plate above, composed of a 

 single series of plates, alternately longer and shorter on 

 the opposite sides ; those in the upper part of the arms 

 larger and somewhat squamous, the upper edge projecting. 

 Tentacula arising from the longest side, apparently short 

 and strong. Surface of plates smooth. Column small, 

 round, composed of unequal plates. 



This small and beautiful species resembles, in the ap- 

 pearance of the calyx, specimens of the genus Dichocrinus ; 

 but the base being distinctly divided into three parts places 

 it in the genus Platycrinus. 



Geological formation arid locality. Burlington limestone, 

 Burlington, Iowa. 



Platycrinus clylis (n. s.). Body small, broadly cup- 

 shaped. Basal plates proportionally large, forming about 

 one third the height of the cup. Radial plates quadangu- 

 lar, height and width nearly equal ; articulating scar small, 

 occupying about one half the diameter of the plate, and 

 extending but a short distance upon the body of the plate. 



