192 PALAEONTOLOGY OF ILLINOIS. 



upper and lower sides, and are of medium height. Pinnules ex- 

 tremely long, rather stout, closely packed together. They are 

 composed of from 10 to 15 cylindrical joints, about three times 

 as long as wide. 



Interradials apparently five to each side, all forming a part 

 of the ventral surface, which is flat and placed on a level with 

 the inflected upper edges of the first radials. The first range 

 of interradials consists of three plates, two of them facing the 

 adjoining radial; the third placed between the two others. 

 There seem to be two, perhaps more, small interradials above, 

 meeting with the summit plates. The azygous side apparently 

 has 5 plates in the lower range, the middle one being an anal 

 plate. The summit plates their exact arrangement could not 

 be ascertained are scarcely convex, they form together a con- 

 spicuous elevation, from which six well defined ridges pass out 

 to the sides; five of them divide again and follow the arms, the 

 sixth one leads to the anal aperture, which is directed upwards 

 and excentric in position. The ambulacral ridges, those lead- 

 ing to the arms, are formed of irregular covering pieces, the 

 anal ridge by numerous convex or wrinkled plates. Between 

 the ridges are six depressions, four of them located above the 

 regular interradii, the two smaller ones above the azygous side. 



The column of this species is not very long. From our ob- 

 servation in two specimens it varies from 9 to 10 inches. The 

 joints increase at first a little in width, but soon taper again, 

 until at the distal end the column runs to a fine point, giving 

 off at intervals a small, short cirrhus from one side only. The 

 joints throughout are very even, and the nodal joints can be 

 distinguished only along the upper part of the stem. Axial 

 canal minute. 



Geological position, etc.: The same as in the last species. 



Our own collection. 



