760 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
set, bead-like processes, which give to the ridges a somewhat serrated aspect. 
Suture lines obscure. . 
Basals large, occupying two fifths to one half the height of the dorsal 
cup, their lower ends projecting into a salient margin; their surface covered 
with eight ridges, six of them radiating from the column to the six salient 
angles which form the upper margin of the dorsal cup; the two others 
follow the interbasal suture. Radials as long as their width at the top, the 
median portions obtusely angular, projecting outward, especially in the 
upper part, where the outer margins of the plates: form a depression or 
groove along the interradial sutures; the outer edges of the facets sur- 
rounded by a large, quite prominent, thickened rim, from which two ridges 
pass out to the lower angles of the plates. The spaces between these ridges 
and those of the basals are marked with a few small nodes, which below the 
basi-radial suture are arranged in transverse lines. The upper lateral angles 
of the radials are not truncated, and the facets are shallow. Anal plate 
similar in form to the radials, but narrower and angular at the top. Costals 
two, short, and closely united. Distichals three; the length of the two 
lower plates together about equal to that of the third. Arms four to the 
ray, subcylindrical, very little tapering; composed of two rows of rather 
large interlocking pieces. Pinnules long. Structure of the disk not known. 
Column round and of moderate thickness; the joints very even and short 
near the calyx, but growing longer downward, and the nodal joints project- 
ing above the internodals. 
Horizon and Locality. — Upper Burlington limestone; Burlington, Iowa. 
Type in the University Museum at Ann Arbor, Michigan. 
Dichocrinus ovatus O. and Suum. 
Plate LX XVI. Fig. 7, and Plate LXXVIT. Figs. 8a, 6. 
1852. Owxn and Saumarp; U.S. Geol. Rep. Wisc., Iowa and Minn., Part II., p. 590, Plate 5.4, Figs. 
lai. Wd, 
1881. W. and Sp.; Revision Paleocr., Part II., p. 84. 
Form of calyx ovoid, higher than wide, widest across the middle of the 
radials; the edges of the plates slightly beveled, and the suture lines well 
defined; plates strong. The basals form a rounded, somewhat conical cup, 
which at its lower end is truncated and slightly excavated. The truncated 
part is completely filled by the upper face of the column, and there is around 
its edge a ring of well defined spinous nodes. The sides of the cup: are 
