7 
ACTINOCRINID A. 579 
They are closed ventrally by two rows of small, irregular side-pieces, which 
rest upon the inflected edges of the brachials, and enclose a single row of 
rather large, cuneate, spinous covering pieces, alternately arranged. The 
upper angle of the brachials is irregular in position, the side bearing the arm 
considerably shorter and distinctly sloping, the other one, supporting the 
next brachial, horizontal. The arms are given off at the sides, the proximal 
joint resting upon the axillary below, and against the truncated lower face 
of the plate above; they are much smaller than the trunks, biserial, and 
pinnule-bearing. In all other points the genus resembles Actinocrinus. 
Distribution. — Known only from America, and here only from the Kin- 
derhook group and Burlington limestone. 
Type of the genus: Steganocrinus pentagonus. 
Steganocrinus pentagonus (Hax1r). 
Plate LXT. figs. Sa to e; and 4a, b. 
1858. Actinocrinus pentagonus — Haru; Geol. Rep. Iowa, Vol. L., Part II., p. 577, Plate 10, Figs. 6a, 0. 
1866. Steganocrinus pentagonus — Mxxx and WortHun; Geol. Rep. Illinois, Vol. II., p. 196. 
1868. Steganocrinus pentagonus —Muzx and Wortuen; ibid., Vol. IIL., p. 474, Plate 16, Fig. 8. 
1881. Steganocrinus pentagonus — W. and Sr.; Revision Paleocr , Part II., p. 151. 
Calyx of medium size, wider than high, distinctly pentangular in its 
dorsal and ventral aspect. Dorsal cup nearly twice as high as the tegmen, 
its sides slightly convex to the top of the first costals, the second costals and 
distichals bent abruptly outward, the latter to a horizontal position, forming 
five calycine extensions, which bifurcate from the second costals into two 
free trunks, which bear arms alternately from each side. Plates of the cup 
thin and but very little convex; their surfaces marked by radiating ridges, 
which meet in the centre of the plates, where they form small nodes. The 
ridges are in single series, except between the radials and basals, where 
there are two. 
Basals rather small, forming a short, rapidly spreading cup without pro- 
jecting marginal rim; the suture lines slightly grooved. Radials and first 
costals proportionally large, about as long as wide, the latter a little the 
smaller, and their sides inflected at the upper end to receive the second 
costals, which are small and distinctly rounded on the back. Distichals 2 X 2, 
connected laterally, about half the size of the upper costals, and twice as 
wide as long, each giving off an arm laterally, one from the one side, the 
