7 



as wide, about two-tbirds as large as the first and hexagonal. 

 Third primary radials a little smaller than the second, wider than 

 long, pentagonal, axillary, and bear upon each superior sloping 

 side a single secondary radial, which is axillary and in one of the 

 lateral rays supports, upon each upper sloping side, one or two 

 tertiary radials, which gives to this ray four arms. In each of the 

 other four rays, one of the proximal sides of the secondary radials 

 bears a tertiary radial, which is axillary, and supports, on each 

 upper sloping side, a quaternary plate, which arrangement gives 

 to each of these four rays five arms. There are, therefore, in this 

 species, twenty-four arms and twenty- four ambulacral openings to 

 the vault. 



The interradial areas connect with the vault. There are six 

 plates in each regular interradial area. The first one is about the 

 size of a second primary radial; it is followed by two smaller 

 plates, in the second racge, and these by two plates, less than 

 one- third as large, in the third range, and above these, one quite 

 small and narrow plate separates the tertiary radials. There is a 

 small intersecondary plate in some of the areas, but it does not 

 connect with the vault. There are ten plates in the azygous area. 

 The first one is in line with the first primary radials, but some- 

 what smaller. It is followed by two plates, in the second range, 

 three in the third, three in the fourth, and one in the fifth range 

 that unites with the plates of the vault. 



The vault is very highly convex and bears a central proboscis. 

 It is covered with numerous polygonal plates, more than half of 

 which bear long robust spines. 



This is the first twenty-four armed Adinocriniis ever described, 

 from any group of rocks, and while, in general outline, it bears 

 some resemblance to Actinocrinus fossalus, a forty-armed species, 

 yet the differences are so manifest that it would be idle to draw 

 any comparison between the two. 



It was found by the indefatigable collector, R. A. Blair, in the 

 Burlington Group, at Sedalia, Missouri, and is now in the collec- 

 tion of S. A. Miller. 



