422 PALEONTOLOGY OF ILLINOIS. 



supports one side of another anal above. Second anal of 

 nearly the same size as the first, and resting upon the supe- 

 rior truncated side of the subradial below. Above these, 

 two alternating series of anal pieces are seen extending 

 upward, to connect with the base of the so-called pro- 

 boscis. 



Arms nine, simple from their origin on the third radials, 

 rather angular on the back, and each composed of short 

 wedge-formed pieces, arranged somewhat in zigzag, with 

 their longer ends alternately on opposite sides, and pro- 

 jecting so as to support stout, rounded pinnule, composed 

 of joints sometimes nearly as long as wide. PinnulsB 

 very regularly arranged, so as to leave intervening spaces 

 scarcely of their own breadth, and so stout as to present 

 rather the appearance of armlets, than Avhat are usually 

 called tentacles, in the descriptions of fossil Criiioids; all 

 like the arms with the ambulacra! furrows comparatively 

 deep and large. 



Vault unknown ; proboscis (so-called) about half as long 

 as the arms, comparatively rather slender until at the upper 

 extremity, where it is suddenly expanded to nearly twice 

 its breadth below, and somewhat flattened on top. The 

 expansion, however, seems to be mainly due to the greater 

 thickness of the plates here than to a corresponding in- 

 crease in the size of the cavity within. Plates of the pro- 

 boscis of moderate size, and all indented at their corners. 



Hight of body to the top of first radial pieces, 0.18 inch; 

 breadth about 0.32 inch; length of arms beyond the top of 

 the third radials, 1.68 inches; length of proboscis above the 

 first radials, 0.95 inch. 



This species is so distinct from all others kiiown to us that it is 

 scarcely necessary to compare it with any of them. It seems to be 

 most like S. Halli, Hall, but differs in having its subradials so tumid as 

 to give the body a truncated appearance below, instead of an inversely 

 carnpanulate outline. Its pinnulse are also much stouter and less 

 oblique, while its arms are entirely without the little flattened spine- 



