HEXACRINID &. TEA 
Basals large, occupying fully one third the height of the calyx, and form- 
ing a rounded cup with obtuse angles upon the upper face; the column facet 
circular and slightly projecting. Radials one quarter to one half longer than 
wide, a little contracted at their lower ends, somewhat bulging at the middle 
portions, and abruptly inflected at the upper; facets less than half the width 
of the plates. Anal piece about the size of the radials, but narrower at the 
top and more distinctly bulging. Costals two, small; the first quadrangular, 
twice as wide as long; the second a little larger and triangular, the upper 
angle rather sharply pointed and bending inward, its sloping sides concave. 
The line of union between the two costals, compared with those above and 
below, quite obscure, constituting a syzygy, the epizygal joint supporting an 
arm. A second syzygy unites the two proximal arm plates, with a pinnule 
given off from the second. Arms two to the ray, twice or three times as 
long as the calyx, comparatively stout, tapering to the tips, and biserial from 
the third plate up. Arm plates of moderate length, with faces transversely 
parallel; the two series united by a zigzae suture. Pinnules extremely long, 
rather stout and closely packed; they are composed of from ten to fourteen 
joints, about three times as long as wide. Plates of the regular interradial 
series three and two, all forming a part of the ventral disk. The anal side 
has five plates in the lower range. Orals arranged in the usual way; the 
posterior one largest and pushed in between the other four. They form 
a slight elevation, from which six well defined ridges pass out to the margin, 
five of them ambulacral, which divide and follow the arms; the sixth con- 
nects with the anus; the ambulacral ridges are composed of two rows of 
irregular pieces. The column in several perfect specimens averages eight 
to nine inches in length; it terminates in a fine point, and gives off at inter- 
vals, one by one, short cirri. All stem Joints, except close to the calyx, are 
of equal length, and the older or nodal joints cannot be distinguished from 
the intervening younger ones. Axial canal minute. 
Horizon and Locality. — Kinderhook group; Le Grand, Marshall Co., 
Towa, where it is one of the most abundant species. 
Types in the collection of Wachsmuth and Springer. 
