PALEOCRINOIDEA. 



GENUS POTERIOCKEsTUS, Miller. 

 POTERIOCRINUS coxANUS, Worthen. 



PI. XXVII, Fig. 1. 



Poteriocrinus Coxanus, WOBTHEN, February, 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 4. 



Body above the medium size, obconic, gradually swelling from a 

 truncated base to the summit of the radial plates, where it is about 

 one-fourth wider than high. Basal plates as wide, or a little wider, 

 than high, forming by themselves a low pentagonal cup, about twice 

 as wide as high. One subradial on the anterior side is longer than 

 wide, the others about as wide as long, all pentagonal, there being 

 but two distinct angles on their lower margins. 



Kadials nearly once and a half as wide as high on the anterior 

 rays, curving in on their lateral borders so as to give a pentalobate 

 character to the upper part of the body. 



Brachials two, the first quadrangular, and the second pentangular, 

 and both more than twice as wide as long, the second supporting 

 on their sloping sides the first divisions of the rays. Only two of 

 the rays and a part of the third are to be seen, the others being 

 concealed in the rock. In one of these, probably the anterior ray, 

 a second bifurcation takes place on the fifth plate in each division, 

 and the outer branch is seen to divide once more about the tenth 

 plate, and the inner division on the twenty-fourth to the twenty- 

 sixth plate, beyond which the arms of this ray are not preserved. 



On the right autero-lateral ray the second bifurcation takes place 

 on the fourth plate in each division, the outer branch dividing twice 

 more on the eighth and twenty-second plate, and the inner one twice 

 on the twenty-fourth to the twenty-sixth plate, beyond which they 

 are not preserved. This gives twelve visible arms to this ray, and 

 it is quite possible there were other divisions beyond, as the arms 

 extended about two inches beyond the last divisions that are pre- 



