608 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
packed, the joints longer, the spmes more slender, and directed more nearly 
outward. Interbrachials in three rows; at the regular sides 1, 2, 1; at the 
anal side 2, 3, 2, sometimes with a small plate wedged in between the pal- 
mars, but generally the palmars are in contact laterally all around. Inter- 
distichals 1 or 2, longitudinally arranged. Ventral disk high, convex; the c 
orals and radial dome plates, which are represented by plates of a first, | 
second, and third order, large and spinous; the interambulacrals not very | 
numerous, smaller and convex. Anal tube central, large and long, extend- 
ing beyond the tips of the arms, and composed of irregular scale-like plates. 
Column of medium side; axial canal rather small. 
Forizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 
Type in the University Museum at Ann Arbor. 
Remarks. — In a very young specimen, evidently of this species, the | 
brachials are free from above the distichals; the palmars and post-palmars 
are more elongate in proportion, and uniserial and cuneate to the third plate, 
resembling in their outlines the arm plates of certain Poteriocrinide. The 
biserial plates above are also proportionally larger than in the older speci- 
mens, but have already the characteristic ornamentation of this species. 
Cactocrinus limabrachiatus (Hatz). 
Plate LVITL. Figs. 9 and 10a, b. 
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1861. <Actinocrinus limabrachiatus — Hatt; Descr. New Spec. Pal. Crin., p. 2; also Boston Journ. Nat. 
rishi (Viol: V LE; p.268. 
1881. <Actinocrinus limabrachiatus — W. and Sv.; Revision Paleocr., Part II., p. 144. | 
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f 
f 
Calyx bell-shaped, one third higher than wide, the arm bases slightly 
projecting ; the dorsal cup fully once and a half as high as the ventral disk. 
Surface of plates traversed by single series of angular ridges, continued from 
plate to plate, and meeting at the centres, where they form sharp nodes. 
Only the basals and radials are connected with one another by four or five 
parallel ridges. 
Basals rather large for the genus, forming a spreading cup; the suture 
lines not grooved. Radials a little longer than wide, their sloping upper 
faces small. First costals short, quadrangular, rarely pentangular, the 
upper and lower margins convex; the second a little larger. Distichals | 
and palmars smaller in proportion. Arms six to the ray, given off as in the 
preceding species, distinctly flattened on the back, the three or four proxi- 
mal plates long and cuneate. Higher up, where the arms become biserial, 
