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618 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
slightly projecting outward. Arm openings almost equidistant, the respira- 
tory pores small. Arms eight to the ray, when normally developed, but 
rays with seven or even six arms occur quite frequently ; they are somewhat 
flattened, and composed of two series of transverse, rather short and appar- 
ently smooth pieces. Regular interbrachials: 1, 2,2, 1 in mature speci- 
mens; the first the same size as the first costals, the upper one very narrow, 
and wedged in between the upper row of brachials. Anal plate followed by 
2, 3, 2, and 1 plate. Ventral disk depressed conical, the plates near the 
summit rather large and sharply nodose, those near the arm bases somewhat 
smaller. Anal tube long, moderately thick, composed of short, transverse 
pieces, with sharp, projecting edges. Column of medium size, the joints 
rather short, the nodal ones distinctly angular and slightly projecting. 
Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 
Type in the (Worthen) Illinois State collection. 
ftemarks.— Approaching C. celatus in the form and ornamentation of 
the dorsal cup, but the tegmen of that species is comparatively higher, 
more conical, and the plates of the anal tube are larger and more nodose. 
Cactocrinus coelatus Hatt. 
Plate LIX. Figs. 8, 9. 
1858. Actinocrinus coclatus —Hatt; Geol. Rep. Iowa, Vol. I., Part II., p. 585, Plate 10, Figs. 14a, 3. 
1881. <Actinocrinus coelatus — W. and Sv.; Revision Paleocr., Part IL., p. 148. 
Larger than the preceding species. Calyx short-subfusiform and highly 
ornamented. Dorsal cup one fourth wider than high; uniformly spreading 
from the basals to the top of the arm-bearing brachials. Ventral disk sub- 
conical, almost as high as the cup, the upper part drawn out, and passing 
imperceptibly into the anal tube. The cup ornamented as in C. multi- 
brachiatus, except that the costals are connected among themselves and 
with the radials by three parallel ridges, in place of one, as in that 
species. 
Base short ; the sides neither spreading upward, nor projecting on the 
lower margin; the lower surface sufficiently excavated to enclose the first 
stem joint ; interbasal sutures distinctly grooved. Radials a little wider than 
Jong, and much larger than the costals. The higher brachials arranged 
as in C. multibrachiatus. Arms eight to the ray, slender; gently curving at 
their bases outward and upward; the tips, so far as observed, not incurving, 
