FOSSILS OF THE ST. LOUIS GEOUP. 531 



more or less truncated, and slightly projecting at the edge; 

 each with a broad, very shallow sinns above for the recep- 

 tion of the second radials, more than three-fourths as wide 

 as its upper margin, while the deep impression at the lower 

 angles forms two broad, strong ridges, extending down- 

 ward to connect with those on the subradials; sometimes 

 these terminate near the middle above, in sharp, pinched-up, 

 diverging nodes, or short carina?, while between these and 

 the superior lateral, truncated angles, one or two other 

 sharp prominences are sometimes seen. Second radial 

 pieces extremely short, or almost transversely linear, and 

 not always entirely filling the broad, shallow sinuses in 

 which they rest. Third radials triangular, a little higher 

 in the middle than the first, but wedging to a very thin 

 edge on each side, or even sometimes thinning out so as to 

 let the first brachial pieces rest at their lateral edges partly 

 on the first and partly on the second radials. Anal piece 

 of moderate size, quadrangular in form, a little wider than 

 high, and resting on the upper truncated edge of the hep- 

 tagonal subradial; while its own upper edge is truncated 

 entirely across, nearly on a level with the superior lateral 

 angles of the first radial on each side. Arms two from each 

 ray, rather long, rounded and tapering; very stout below, 

 where they are composed of thin, short, wide pieces, the first 

 two of which in each pair of arms are joined together at their 

 inner ends ; above these the arms of each ray diverge more or 

 less from each other, and throw off alternately, on each side, 

 stout armlets from every second piece. Arm pieces above 

 the wide ones at the base somewhat longer in proportion 

 to breadth than the latter, and more wedge-formed, with 

 each a little pinched up or angular ridge or projection on 

 each side, ranging transversely to the arms, that is, inward 

 and outward. Armlets stout, tapering, and usually about 

 eight or nine to each side of each arm, nearly half avS thick 

 as the arms just above Where they are given off; composed 

 of pieces of nearly the same form as those of the arms, but 



