304 PALEONTOLOGY OF ILLINOIS. 



ZEACBINUS PIKENSIS, Worthen. 



PI. XXX, Fig. 3. 



Zeacrinus Pikensis, WOKTHEN, Feb. 1882. 



Bulletin of the Illinois State Museum of Natural History, p. 29. 



Body of medium size, short, forming below the summit of the radial 

 series a shallow cup about three times as wide as high. Basals small 

 and entirely concealed in the basal concavity. Subradials rather 

 longer than wide, and curving below so as to form a part of the 

 concavity of the base. 



Kadials pentagonal once and a half, and the anterior one prob- 

 ably twice as wide as long, and truncated squarely across their upper 

 margins for the reception of the brachial series. 



The anterior ray has three brachials, ihe first one of which is as 

 large as the radial below, the second one very short, and both 

 quadrangular; the third is also short, but pentangular, supporting 

 on its sloping sides the first divisions of the ray. One of these di- 

 visions bifurcates again on the eighth plate, and the other on the 

 tenth, beyond which they appear to be simple to their extremities, 

 making but four arms to this ray. The right antero-lateral ray and 

 the left posterior ray have each a single brachial, which is nearly 

 as long as wide, supporting on its sloping angles the first divisions 

 of the rays. The two divisions of the right antero-lateral ray divide 

 again on the sixth plate, and at least one of these divisions, and 

 probably both the outer ones, divide again on the tenth plate, making 

 six arms to this ray. If the other rays correspond with this, it would 

 give twenty-eight arms as the full series for this species. Anal plates 

 unknown. Column slender, and composed of round joints of unequal 

 thickness. 



Geological position and locality: Lower part of the Burlington lime- 

 stone, Montezuma, Pike county, Illinois. 

 No. 2,462, Illinois State collection. 



