31 



The vault is subpyramidal and flattened in the interradial areas. 

 There is a large tumid plate, at the apex of the vault, which is 

 surrounded by six large convex plates and three small plates, at 

 the top of the azygous area. There is a single large tumid plat*; 

 over the lower part of each ambulacral area. These large plates 

 cover the ambulacral canals, where they unite, in each radial 

 series. All other plates in the vault are smaller than those de- 

 scribed, polygonal, vary much in size, some are convex but they 

 are generally flat. The azygous area is covered with numerous 

 small plates, is longitudinally convex centrally and hus an azygous 

 opening in the superior part of the central elevation. 



This species is distinguished from all others heretofore described 

 by the number and form of the regular interradials, by the num- 

 ber and form of the azygous plates and by having ten arms. 

 Other differences are conspicuous when it is compared with other 

 ten-armed species. 



Found by Prof. A. G. Wetherby, in the Keokuk Group, in Ten- 

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



CYLrCOCRINUS (?) INPIANENSIS, n. sp. 



Plate 1 V, Fig. 20, basal view; Fig. 21, azygous side; Fig. 22, 



opposite view. 



There is doubt about the generic reference of this species, but, 

 notwithstanding the wide variation from the type species, in the 

 absence of a knowledge of the vault, we have concluded so to refer 

 it, rather than to coin a new generic name. The calyx is broadly 

 rounded below and slightly constricted toward the top, though 

 somewhat semi-elliptical, in outline. Width about one and a half 

 times the height. Plates convex and more or less nodose. Column 

 small and round. 



Basals three, equal, and forming an hexagonal disc having three 

 re-entering angles and having a width from three to four times 

 the diameter of the column. Each basal plate bears two spines 

 that are directed downward around the column, and, upon thf3 

 apices of which, the calyx will stand. The first primary radials 

 are very large, a little wider than high, three hexagonal, two hep- 

 tagonal. Second primary radials quadrangular and more than 

 twice as wide as high. Third primary radials about the same 

 size as the second, pentagonal, axillary and support on each upper 

 sloping side the secondary radials. Our specimen preserves only 

 one secondary radial in each series, but, as it does not show an 

 ambulacral notch, it is believed there are two and that the second 



