10 



by a raised ridge running from a central tubercle on each first 

 radial to another, so as to bound the columnar cavity with a raised 

 pentagonal figure. We have illustrated a basal view to show this 

 pentagonal outline, because Lyon's figure does not show its pen- 

 tagonal character. 



The basal plates are deeply sunken. First primary radials in- 

 cluding the extension into the columnar cavity longer than wide; 

 ornamented with sculptured ridges, which terminate at a central 

 node, at each angle of the columnar depression. Second radials 

 quandrangular, wider than high, and bearing a central node. Third 

 radials pentagonal, wider than high, and bearing a central node. 

 First secondary radials as large or larger than the third primary 

 radials. Second secondary radials much smaller and of irregular 

 form and size. Third secondary radials still smaller and of irreg- 

 ular form and size. Arms, ten, composed of ovoid flat pieces of 

 equal thickness. 



First inter radials the larger plates of the calyx, nine- sided, sub- 

 ovate, angularly pointed below and resting between the upper slop- 

 ing sides of the first primary radials, the upper sloping sides separate 

 the first secondary radials and the superior side is truncated for a 

 single plate in the second range. Second interradials subquadrate, 

 four pentagonal and one quandrangular and followed by two small 

 plates in the third range (in some areas there are three) and 

 these by three smaller, elongated plates (sometimes there are only 

 two) that separate the arms and unite with the plates of the vault. 

 Intersecondary plates, two, similar to the last three in the inter- 

 radial areas, and separating the arm bases and uniting with the 

 plates of the vault. Above the summit of the three inter- 

 secondary plates and also above the summit of the last two or 

 three interradials, two elongated pores or passages penetrate the 

 vault horizontally. In some interradial areas there are four of 

 these pores, especially where there are three plates in the third 

 range. These pores are conspicuous, in our specimens, but they 

 seem to have been entirely overlooked by Lyon, for they are not 

 shown in his illustration or mentioned in his text. We have given 

 a side view of a specimen for the purpose of showing the inter- 

 radials and intersecondary plates and the pores, because Lyon's 

 illustration is very erroneous and defective, in all these respects. 



Found in the Upper Helderberg Group, at the Falls of the Ohio, 

 and in Clark County, Indiana. 



