13 



The vault is, convex and covered with numerous, more or less 

 convex, polygonal plates. It bears a subcentral proboscis. The 

 arm openings are directed upward and are visible in a summit 

 view. No ovarian pores discovered. 



This is the first twenty-one armed Actinocrinus ever described 

 from the Burlington Group, and hence there is no necessity for 

 comparing it with any other species. Indeed, it is so far removed 

 from all other species, in its essential structure, that it would be 

 difficult to make a comparison with any of them. 



Found in the Burlington Group, at Burlington, Iowa, and now 

 in the collection of Wm. F. E. Gurley. 



ACTINOCRINUS SUBPULCHELLUS, n. Sp. 



Plate III, fig. 12, azygous side; fig. 13, opposite view; fig. 14, 



summit. 



Species medium or below medium size. Calyx obpyramidal, one- 

 third wider than high, moderately truncated below, pentagonal 

 above, in transverse section; radial ridges sharp, interradial areas 

 flattened. Plates convex or nodose. 



Basals form a low hexagonal cup, about three times as wide as 

 high. The sutures are beveled, the basals are expanded below, 

 and the sharp, radial ridges are extended across the basals, though 

 not prominent. The first primary radials are as long as wide, 

 three hexagonal, two heptagonal, and each one bears a central 

 node. Second primary radials hexagonal, about two-thirds as large 

 as the first, wider than long. Third primary radials smaller than 

 the second, pentagonal, axillary, and support, on each upper slop- 

 ing side, a single secondary radial which bears the free arms. 

 There are, therefore, ten arms in this species. An intersecondary 

 plate separates each pair of ambulacral openings to the vault. 



The first regular interradials are rather larger than the second 

 primary radials, slightly convex, not nodose. There are two plates 

 in each second range and two in the third range that separate 

 the arm openings and unite with the plates of the vault. The 

 first azygous plate is in line with the first primary radials, of 

 about the same size, and bears a central node. It is followed by 

 two slightty convex plates, in the second range, three in the third 

 range, and five smaller plates in the fourth range that separate 

 the ambulacral openings and unite with the plates of the vault. 



