348 PROCEEDINGS OF THE ACADEMY OP [1879. 



with nearly straight sides, slightly concave in the middle. Basals 

 about of equal size, hexagonal, wider than high. Radials. penta- 

 gonal, wide, and short, broadly truncate above. Brachials one 

 by five, similar in form to the radials, but truncate below instead 

 of above; they support on each upper sloping side an arm which 

 bifurcates on the fourth to the eighth plate above, the branches 

 remaining simple throughout, thus giving four arms to each ray 

 uniformly. 



The ax*ms are rather divergent, heavy, rounded on the outside, 

 gently tapering to the tips and terminating in a sharp point. 

 Arm pieces extremely short, their sutures parallel. Pinnulae long 

 and numerous, directed inward, composed of ten to twelve small 

 joints. 



The anal area is remarkable for its great number of pieces, 

 being composed longitudinally of several rows of plates, alter- 

 nately arranged. The lower and largest plate rests between two 

 basals, one of the upper sides against the right posterior ra- 

 dial, the other against the first anal of the adjoining row. The 

 second anal plate rests upon a basal, and abuts laterally against 

 the left posterior radial. The third anal is placed upon the first, 

 toward the right side of the second, and rests partly against the 

 right posterior radial. The anal area is elliptic in outline, com- 

 posed of twelve or more plates, only three of which are on a level 

 with the radials. The form of the ventral sac is unknown, but 

 from all appearances it is somewhat balloon-shaped, and does not 

 extend to the top of the arms. 



Column rather slender, composed of alternate wider and nar- 

 rower joints, their diameter increasing from the root up, being 

 largest next to the calyx ; central perforation round. 



The genus is from the Subcarboniferous, and the only known 

 species is : 



1854. Woodocrinus macro dactylus De Koninck. Recherch. Crin. Belg. Supple- 

 ment, p. 6, pi. 8, figs. 1 a-d. Upper part of Subcarb. Richmond, England. 



17. ZEACRINUS Troost. 



1850. Zeacrinus Troost. Subgenus of Poteriocrinus. Cat. Crin. Tenn., p. 



62 (without description.) 

 1858. Zeacrinus Hall. Subgenus of Poteriocrinus. Geol. Rep. Iowa, vol. 



i. pi. 2, p. 544. 



