404 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
the upper one very short, leaf-like, and supporting the arms, except in the 
two posterior rays, in which the distichal next to the anal side is axillary, 
and supports on each side a single palmar, thus making the number of arms 
in these rays three, against two in the three others. Arm facets very large, 
directed obliquely upwards. Ambulacral openings elongate, arranged in 
groups, the interspaces between the rays twice as wide as those between 
their subdivisions, and at the posterior side almost three times as wide, and 
somewhat depressed. Structure of arms not known, but, to judge from the 
size of the facets, they were unusually stout, and were biserial from their 
origin. Interbrachials one, elongate, very large, arched by the arm-bearing 
brachials. Anal plate longer than the radials, the lower angle sharp and 
extending far down into the basal disk ; 1t is followed by three large plates, 
and there is a smaller one between the palmars, which connects with the 
interambulacral pieces above. A similar small plate occurs exceptionally 
between the distichals at the other sides. Ventral disk depressed hemi- 
spherical. The orals are raised into short spines or sharp nodes; the posterior 
one central in position, a little larger, and less spinous. The radial dome 
plates, which are fully as large as the orals, and are also extended into 
spinous nodes, are placed around the periphery; there is one of these plates 
over the anterior and each antero-lateral ray, and three over the two poste- 
rior ones; the spines are directed slightly outward, and give to the tegmen 
that peculiar coronate aspect which is so characteristic of this species. Inter- 
ambulacral plates small, and merely convex. Anal tube subcentral, very 
small at the base, its length not known. 
Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 
Type in the (Worthen) Illinois State collection. 
Eretmocrinus intermedius W. and Sp. 
Plate XX XIII. Figs. 2a, 6, c. 
1881. W. and Sp.; Revision Paleocr., Part II., p. 174. 
A small species. Dorsal cup broadly truncate at the bottom, the sides 
straight or slightly convex. Plates almost flat; the radial ones marked by 
indistinct ridges, which pass into the arms; the interradial plates covered 
with a small central node, and all obscurely fluted toward their margins. 
Base short, broad, slightly projecting laterally, rounded along the margin, 
indistinctly grooved at the sutures, the lower surface excavated, and to one 
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