516 PALEONTOLOGY OF ILLINOIS. 



surface markings will serve to distinguish it from any other species of the 

 genus at present known in the Lower Carboniferous limestone. Arms 

 and column unknown. 



Position and locality : Otter creek, Jersey county, Illinois; Keokuk 

 limestone, Lower Carboniferous. 



Genus POTEEIOCKINUS. 

 Potekiocrintts Hoveyi, Worthen. 



PI. 29, Fig. 6. 



Body below the second radials obconical and tapering very gradually 

 from the top of the first radials to the column. Base nearly twice as 

 wide at the top as long, truncated below the breadth of the column ; 

 basal plates longer than wide, pentagonal in form, with salient angles 

 above ; subradials comparatively large, length and breadth about equal, 

 and, so far as can be seen in the specimen under examination, hexago- 

 nal; first radial plates smaller than the subradials, pentagonal and 

 truncated squarely across their upper margins for the reception of the 

 next radial pieces ; second radials a little longer than wide, rounded 

 and slightly constricted in the middle, pentagonal, and supporting the 

 arms on their superior sloping sides. 



Arms very long, two to each ray in two of the rays seen, and one only 

 in the other or anterior ray (as in P. Coryi), and composed of rather 

 short, rounded, wedge-shaped pieces, and giving off long slender pin- 

 nulce to their extremities. Ventral tube very long, cylindrical, composed 

 of rather large plates with short, stout spines at the summit. Column 

 round and composed of rather thin plates at the base. 



Position and locality : CrawfordsvilJe, Indiana, in shales of the Keo- 

 kuk group, Lower Carboniferous. 



I take pleasure in dedicating this fine species to Prof. E. O. Hovey, 

 of Wabash College, Crawfordsville, Indiana. 



Potekiocrintjs Cokey-i, Worthen. 



PI. 29, Kg. 2, 3. 



Body below the base of the arms rather deeply cup-shaped or truncato- 

 obconic; basal plates small pentagonal, and projecting about half their 

 length above the truncated base. Subradials moderately large, higher 

 than wide and hexagonal. First radials pentagonal and about once and 

 a half as wide as high, rather smaller than the subradials, and four of 

 them truncated their whole width for the reception of a second radial 

 piece. Second radials less than half as high as the first and rounded 



