J 
t 
i 
) j 
Tj ie a eae linia aes.” 
a WE a a I sath, 
— — —e ae a . 
TE aT ; Whe —as = ir, = X ‘ 
a ee we — as —- ——— = ——== ‘ 
% 
. : a 6 
= eh 
- — 4 : 
a 
a <_< en ——— 2 reuaasta —t - ’ aaa == eos = ne > 
Ca ime te f ~ som = —— a Fa aa - a {a ee, ee - 
iat ti) — Tee , Rr eo 5 Om "i =~ ‘ A 
= — in — ee ——~ cen : Se secon ax - ——— snr a be ; 
=~ om i. f yin As : 
482 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
the back, very stout, widest at midway, somewhat tapering at both ends, the 
tips infolding. The free arm plates are elevated in the centre, and produced 
into transverse angular ridges, which in the upper part of the arm are broken 
into nodes. There is but a single interbrachial at the regular sides; the 
anal side has two, which enclose a second anal. The first anal is a little 
longer than the radials. The exact arrangement of the plates in the tegmen 
cannot be accurately ascertained from any of the specimens. Column com- 
paratively strong; the nodal joints a little highest and widest, and rounded 
at their edges. 
Horizon and Locality. — Waverly sandstone; Richfield, Summit Co., and 
Royalton, Cuyahoga Co., Ohio. (Fig. 2 is made after Hall, Fig. 5 drawn from 
a gutta percha cast made in a natural mould.) 
Aorocrinus concavus (Mesx and WorrTHey). 
Plate XL. Figs. 13a, b, ¢. 
1861. <Actinocrinus (Amphoracrinus) concavus — MEEK and WortHEN; Proceed. Acad. Nat. Sci. Phila., 
1865. ere (Spherocrinus) concavus — M. and W.; ibid., p. 154. 
1865. Actinocrinus (Calocrinus) concavus—M. and W.; ibid., p. 273. 
1866. Cclocrinus concavus — M. and W; Geol. Rep. Ilhnois, Vol. IL., p. 215, Plate 15, Figs. 10a, 4, ec. 
1881. Doryerinus concavus —W. and Sp.; Revision Paleocr., Part I1., p. 179 (Proceed. Acad. Nat. Sci. 
Phila., p. 358). 
A small species. Calyx subglobose, wider than high; the ventral disk 
almost flat. The sides of the dorsal cup rise nearly vertically from the 
middle of the radials to the arm regions; the lower half curving abruptly 
inward, and forming with the basals the bottom of the cup. The plates are 
nearly flat and devoid of ornamentation. 
Basals small, spreading almost horizontally, and forming a shallow in- 
verted basin, which is slightly notched at the sutures. Radials extremely 
large, fully twice the size of both costals together. Costals very small, quad- 
rangular and pentangular. Distichals 1 X 2, supporting the arms, except in 
the posterior rays, in which the divisions next to the anal area support pal- 
mars, and there are three arms to the ray in place of two in the others. Arm 
openings small, directed outward; the structure of the arms not known. 
The interbrachials consist of one large plate and two smaller ones, the latter 
being on a level with the arm bases. First anal larger than the radials ; 
followed by three rows of three plates each, which decrease in size upwards, 
and connect with the anal opening. Tegmen very short, a little depressed 
