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ACTINOCRINID.®. 615 
and costals of nearly the same size, and all a little wider than long; the 
distichals of the same form, and but slightly smaller; the palmars about half 
the size of the distichals. The outer palmars of each ray support an arm, 
the inner ones two small post-palmars and two arms. Arms crowded, long, 
rather heavy throughout, rounded on the back, their upper parts incurving, 
their proximal ends bending almost horizontally outward. Interbrachials 
five at the regular sides: 1, 2, 2; and there are 2, 3, and 2 above the anal 
plate. Some specimens have an additional narrow piece wedged in between 
the palmars. Interdistichals one. Ventral disk conical, slightly expanding 
near the arm bases, then rising evenly, and passing insensibly into the anal 
tube. The plates close to the arm regions are very small and almost flat, 
higher up larger and nodose plates are interposed between smaller ones, and 
at the foot of the anal tube all the plates are large and sharply nodose. 
Anal tube long, extending beyond the arms; composed of rather large, 
convex pieces, which decrease in size with the tube. 
Horizon and Locality. — Same as last. 
Cactocrinus sexarmatus (Hatz). 
Plate LV. Figs. 10 and 11. 
1860. Actinocrinus sexarmatus — Warn; Suppl. Geol. Rep. Iowa, p. 21 (not Bull. I., N. Y. State Mus. 
Nat. Hist., 1872, Plate 3.4, Fig. 26 = Cactocrinus extensus W. and Sp.). 
1881. Actinocrinus sexarmatus —W. and Sp.; Revision Paleocr., Part II., p. 145. 
Readily distinguished from the other species of this genus by the form of 
the calyx, which is biturbinate ; the arm bases are not spreading, and the 
arm openings directed obliquely upwards. Dorsal cup deeply bowl-shaped, 
truncate at the base, the sides slightly convex below, and straight above. 
Plates but little elevated, their middle portions flat and perfectly smooth; 
but they are connected with adjoining pieces by short, prominent ridges, 
which form deep, trigonal pits at the angles of the plates. 
Basals trilobate, short but wide, and somewhat spreading outward; the 
lower surface a little excavated for the reception of the column, which occu- 
pies about half its diameter. Radials very large, nearly as long as wide, 
and nearly as large as both costals together. First costals hexagonal, one 
fourth wider than long; the second about the same size as the first, but 
heptagonal. Distichals, palmars, and post-palmars rapidly decreasing in size 
upward, the first post-palmars elongate and semi-free. Arms six to the ray, 
the outer palmars of the rays being axillary. The structure of the arms is 
