ACTINOCRINID &. Sybil 
Actinocrinus tenuisculptus McCursyry. 
Plate LV., Higs. 4a, b. 
1859. McCursney; Descr. New Spec. Paleoz. Foss., p. 15. 
1867. McCuesney; Trans. Chic. Acad. Sci. Vol. I., p. 11, Plate 5, Fig. 1. 
1881. W. and Sp.; Revision Paleocr., Part II., p. 146. 
Syn. Actinocrinus chloris Hau —1861; Boston Journ. Nat. Hist., Vol. VIL, p. 275. 
A moderately small species, which, in the delicacy of the plates of the 
calyx, the beauty of their ornamentation, the spiniferous character of the 
plates in the tegmen, and the long hooks upon the pinnule joints, reminds 
us of certain forms for which we have proposed the genus Cactocrinus. The 
calyx, however, is distinctly lobed, and the arms are arranged in clusters, 
which are separated by wide and deep depressions or grooves extending far 
up into the ventral disk, and the upper bifurcations of the ray take place 
from two successive palmars. Dorsal cup semiglobose, truncate at the base, 
with a small rim around the lower margin, the sides convex to the top of 
the distichals, thence slightly more spreading to the arm bases. Tegmen 
almost as high as the dorsal cup, subpyramidal; cross-section at the arm bases | 
broadly quinquelobate. Plates of the dorsal cup slightly tumid, covered 
by radiating ridges with undulated edges, wider at the middle of the plates 
than at their margins. The ridges passing up and down the radials and 
brachials considerably the strongest, dividing the surface of the calyx into 
five well defined fields, which extend from the basal ring to the bases of the 
free arms, and enclose a well marked star at the four regular sides, while the 
anal side contains two somewhat smaller stars with seven rays. 
Basals short, the projecting rim subcircular or obscurely trilobate, accord- | 
ing to the greater or less depth of the sutural depression. Radials from 
one fifth to one third wider than long. First costals half the size of the 
radials, quadrangular, and nearly twice as wide as long; the second hep- 
tangular, wider and longer in proportion, obtusely angular above. Distichals 
rather small, all axillary, giving off an arm to the outer side, and two small 
palmars which support two arms to the other. Arm facets small, but the 
ambulacral openings comparatively large. Arms six to the ray, slightly 
angular below, gradually flattening above; the tips incurving. ‘The four 
proximal arm joints are in single series, as long as wide, and even longer; 
they are cuneate, and each one has at its upper end from its longer side 
