7! 



with angular ridges and furrows as follows: An angular ridge 

 extends from each angle of the basal disc to the columnar de- 

 pression, and two or three ridges parallel with each side of the 

 disc, are arranged between them; and, on each first radial, an 

 angular ridge extends from each lower lateral angle, from one- 

 half to two- thirds the length of the plate, to a constriction, or 

 subcircular furrow, and these ridges are connected by three 

 ridges parallel with the lower side, and there are three ridges 

 between the subcircular furrow and each perpendicular suture. 



Basals form a pentagonal disc, not higher than the thickness 

 of the plates, with a concave depression in the central part, 

 where the column attached; and sculptured as above described, 

 though the sculpturing becomes less defined as it approaches 

 the concave depression. First radials project, in the lower 

 part, at an angle of about forty degrees; but, the superior part, 

 beyond the constriction, is directed horizontally, and the facet, 

 for the second plate is transverse, or nearly perpendicular, 

 with a notch for the ambulacral canal. Surface ornamentation 

 as above described. The angles for the reception of the inter - 

 radials are more acute than is usual in this genus. There is 

 only a single regular interradial, in each area, and it forms 

 part of the vault. 



Vault elevated and convex toward the central part, so as to 

 have a capacity equal to or greater than the calyx. A single 

 large spinous plate occupies the central part; it is surrounded 

 with eight plates, six of which bear spines and the other two 

 abut upon the azygous orifice. Each plate over the junction of 

 the ambulacral canals bears a spine, the other plates are con- 

 vex but not nodose. The azygous area is comparatively large, 

 the first plate is as large as a regular interradial and stands 

 nearly upright, and above on either side of it there are two 

 small plates, and between and above these nine plates surround 

 a large azygous orifice. 



This species is readily distinguished by its general form 

 and surface ornamentation from all heretofore described. 



Found in the Burlington Group, at Sedalia, Missouri, by R. 

 A. Blair, and now in the collection of S. A. Miller. 



