ACTINOCRINIDZ&. 607 
vided with sharp spines from 14 to 2 mm. in length. Regular interbrachials: 
1, 2,2, and 1. The first anal plate supports 2, 8, and 3 plates, and probably 
two more in the upper regions. Of the ventral disk little is known, except 
that it was covered by spinous plates. Column preserved only to the extent 
of a few pieces, which show that the nodal joints near the calyx have sharp, 
distinctly crenulated edges, and that the intervening joints are narrow and 
evenly rounded. 
florizon and Locality. — Same as last. 
Types in the collection of Wachsmuth and Springer. | 
Remarks. — Distinguished from C. reticudatus and allied species by the 
arm formula, and the surface structure of the arms. 
Cactocrinus opusculus (Ha11). 
Plate LVI. Figs. 5a, 0. 
1860. Actinocrinus opusculus — HauL; Suppl. Geol. Rep. Iowa, Plate 2, Fig. 6 (without description). 
1861. <Actinocrinus opusculus — Hat; Boston Journ. Nat. Hist., Vol. VIL, p. 264. 
1881. <Actinocrinus opusculus —W. and Sp.; Revision Paleocr., Part II., p. 144. 
1893. Wuuitrrenp; Mem. Amer. Mus. Nat. Hist. N. York, p. 9, Figs. 6, 7. 
In form and ornamentation closely resembling (@. thetis, but the species is 
smaller, and differs essentially in the surface structure of the arms. Calyx 
higher than wide, attaining its greatest width at and above the arm regions; 
truncated at the base. The dorsal cup quite narrow to the top of the dis- 
tichals, then spreading abruptly, and forming a short rim, somewhat similar 
to that of Strotocrinus, from which the ventral disk rises almost vertically to 
one third its height. Surface of plates convex, traversed by narrow ridges, 
which, passing from the centre of the plates, unite at the edges with those 
of adjoining plates. 
Basals short, thickened at the outer margins, and indented at the suture 
lines; the lower surface deeply excavated ; surface of the plates covered 
with coarse wrinkles. Radials and costals almost twice as wide as long, the 
former somewhat the larger. Distichals a little smaller than the costals. 
Palmars quite small; the two inner ones of each ray supporting two arms; 
the two outer but one. Arms thirty; long, incurving, rounded at the base, 
but almost perfectly flat above, and somewhat wider, the edges knife-like 
and distinctly serrated. The arm plates are transversely angular, arranged 
in parallel rows, each plate marked by a small node placed close to the 
median suture line. Pinnules similar to those of C. clarus, but less closely 
