HETEROCRINIDAE 
I 2 I 
HALYSIOCRINUS Ulrich 
Plates 2g, 50 
Cheirocrinus Hall (not Eichwald), 13th Rep. New York St. Cab., i860, p. 123 . — Halysiocriims Ulrich, 
14th Ann. Rep. Geol. Surv. Minnesota, 1886, p. no. — Bather, Crin. Goth, 1893, p. 61, fig. 131?. — Zittel- 
Eastman, Texth. Pal., 2d ed., 1913, p. 214. 
Arms and stem as in Calceocriniis, except that the axil-arms do not reach 
the extreme stage, and the main branch is always more or less exposed. The 
two segments of 1 . ant. R triangular, and always completely separated by the 
simple radials. Siibanal piece atrophied or hidden, its place being taken by the 
posterior shifting of r. post, and r. ant. inferradials, which have met, support- 
ing anal a' directly. Fused left basal usually convex toward the stem, and nearly 
or quite the full width of hinge. Median arm frequently branching. 
Genotype. Cheirocrinus dactyliis Hall. 
Distribution. Devonian to Carboniferous ; America. 
As stated under Calccocrinus, the first paragraph of the diagnosis of that genus applies 
to this, in which the axil-arm system is equally characteristic, but developed in a somewhat 
different way, the exposure of the main branch being here a constant character, as is also the 
separation of the segments of 1. ant. R. There may also be noted an increasing tendency to 
branching of the median arm. The difference in the structure of the posterior side, marking 
for this genus the final stage in the elimination of the radials of the vanished arms, in which 
their inferradial remnants are pushed to a position directly underneath the anal tube, is a 
reliable criterion ; and tbe greater width and convex form of the fused basal is a useful 
guide in practice, being fairly established in the Devonian and apparently constant in the 
Carboniferous. 
The genus is essentially an American form, being represented by species in the Helder- 
bergian, Onondaga and Hamilton of the Devonian, and the New Providence, Burlington, 
Keokuk and Warsaw of the Lower Carboniferous. It has not thus far been recognized in 
Europe. 
Halysiocrinus keyserensis new species 
Plate 2g, fig. 22 
This earliest known representative of its genus, from the Lower Devonian, 
while it has the predominant outer ramules and the dwarfed main branches 
somewhat exposed, as usual in the genus, differs from the axil-arm type gener- 
ally by having the axillary primibrach and the succeeding main-axils about 
equal-faced. The median arm is long and simple, with brachials moniliform, 
and the axil-arms four in number. The anal plates at base of tube are large 
and broadly rounded, but the tube itself is not exposed. In the nearly equal 
bifurcation upon the main-axils there is some resemblance to Deltacrinus clams 
and Halysiocrinus secundus of the Middle Devonian, as figured and redescribed 
in the recent volume on the Devonian Crinoids of New York, plate 41. 
Based upon a unique specimen from the Keyser formation of the Helderbergian, at 
Keyser, West Virginia. 
