6 



two tertiary radials and no quaternary plates, which gives to this 

 ray five arms. There are, therefore, twenty-nine arms and twenty- 

 nine ambulacral openings to the vault in this species. 



The interradial areas all connect with the plates of the vault. 

 In each regular interradial area the first plate is about the size 

 of a second primary radial. It is followed by two smaller plates 

 in the second range, and these by two smaller plates in the third 

 range, and these by a single elongated plate in the fourth range, 

 in each of three areas, that unites with two plates belonging to 

 the vault. In the other area there are two elongated plates, in 

 the fourth range, that unite with the plates of the vault. There 

 is an elongated plate in each intersecondary area that separates 

 the quaternary plates and unites with the plates of the vault in 

 some of the areas. 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, two in the fourth, and two narrow elongated 

 plates in the fifth range, that unite with the plates of the vault. 



The vault is highly convex, depressed toward the interradial 

 areas, and covered by numerous polygonal plates, about one fourth 

 of which bear spines. The proboscis is central, but broken off in 

 our specimen. 



This is the first twenty-nine armed species described from the 

 Burlington Group, and so different from all thirty-armed species 

 that no comparisou with any of them is nesessary. 



Found by F. A. Sampson, in whose honor the specific name is 

 proposed, in the Burlington Group at Sedalia, Missouri, and now 

 in his collection. Also found by R A. Blair, and in the collection 

 of S. A. Miller. 



ACTINOCRINUS PETTISENSIS, n. sp. 



Plate I, fig. 3, azygous side; fig. 4, opposite view. 



Species medium size. Calyx obconoidal, one-third wider than 

 high, plates convex and rather deeply, radiately sculptured. 



Basals form a low cup, about four times as wide at the top as high. 

 It is truncated below about one-half wider than the diameter of 

 the colum and bears an hemispherical depression for the attach- 

 ment of the column. First primary radials wider than long, three 

 hexagonal, two heptagooal. Second primary radials nearly as loog 



