39 



Calyx low, basin -eh aped below the summit of the first radials, 

 moderately concave below; plates convex; sutures distinct; surface 

 granular. Column round and pierced by a very small, round cen- 

 tral columnar canal. 



Basals form a narrow pentagonal rim around the column about 

 one-half wider than the diameter of the column. Subradials longer 

 than wide, and curve into the basal cencavity ai d upward, at 

 about the middle part, so as (o be visible in a side view. The 

 curve into the basal concavity is abrupt and the middle part of 

 each is depressed before uniting with the basal plates. Four are 

 hexagonal and two heptagon al. First radials about one and a half 

 times as wide as high, pentagonal, truncated the entire width 

 above, and separated from the second radials by a gaping suture. 

 Second radials smaller than the first, about twice as wide as high, 

 pentagonal, and support upon each upper sloping side the secon- 

 dary radials or free arms. There are, therefore, ten arms in this 

 species. The arms are very long, subfusi form, and composed of 

 a single series of short, quadrangular or slightly cuneiform plates. 

 The pinnules are composed of snbcylindrical pieces having a length 

 equal to three diameters. 



The first azygous plate is rather large, convex, pentagonal, rests 

 between two subradials and the first radial on the right and abuts 

 upon the second and third interradials. The second interradial 

 truncates a subradial, is nearly as large as the first, and the suc- 

 ceeding plates ar^ much smaller and alternately arranged as in 

 other species of this genus. 



This species has been confounded with Z. mam'formis, by some 

 collectors, but in that species the basal plates are hidden by the 

 column, the body is shorter, and there are only nine arms, as the 

 radial series opposite the azygous area bears only a single arm. 

 It is still farther removed from all other species. 



Found in the Kaskaskia Group, in Pulaski county, Kentucky, 

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



