420 PALEONTOLOGY OF ILLINOIS. 



Anal series consisting of two alternating vertical ranges 

 of pieces, the first of which rests between the two upper 

 sloping sides of two of the subradials, and supports an in- 

 ferior sloping side of the first radial on the right, while its 

 left side above the middle connects with another anal rest- 

 ing upon the truncated upper side of one of the subradials, 

 and connecting with the first radial on the right. Above 

 these one or two ranges of similar pieces join with those 

 forming the base of the so-called proboscis. 



Arms not positively known to bifurcate after their origin 

 on the second radial pieces ; composed of joints, the lower 

 of which are twice to three times as long as w T ide, and 

 rounded or subangular, and narrower in the middle than at 

 the ends. Above these the pieces gradually become shorter, 

 and more distinctly expanded at the ends, with the upper 

 lateral extremity of each somewhat projecting alternately 

 on opposite sides, so as to present a distinct zigzag arrange- 

 ment, the projection being for the support of the pinnule, 

 which are comparatively rather stout, and composed of 

 joints two or three times as long as wide, and provided with 

 deep ambulacra! furrows within. 



Column comparatively rather stout; subpentagonal near 

 the base, but soon tapering and becoming rounded below; 

 composed below of uniform pieces; about one-third as 

 thick as wide, but gradually becoming thinner near the 

 base of the body. 



Length of the body to top of first radial pieces, 0.17 

 inch ; breadth about 0.22 inch ; length of arms, about 1.10 

 inch. 



This species is related to that we have here described under the name 

 8. nanus, but not only differs in having longer arms, but in having its 

 second radial pieces and all of its arm joints much longer in proportion, 

 as well as presenting a more strongly zigzag arrangement. Its base is 

 also more protuberant, and the sutures between its body plates slightly 

 impressed instead of even. 



