HETEROCRINIDAE 
II5 
CALCEOCRINUS Hall em. Ringueberg 
Plate 2g 
Calceocrinus Hall, Pal. New York, 2, 1852, p. 352, pi. 85, figs. 5, 6; 28th Rep. New York St. Cab. Nat. 
Hist, 1879, P- 146, figs. I, 2; I2th Ann. Rep. Indiana Dep. Geol., 1882, p. 281. — Shumard, Trans. 
Acad. Sci. St. Louis, 2, 1866, p. 358. — Meek and Worthen, Geol. Surv. Illinois, 5, 1873, pp. 443, 502, 
pi. 14, fig. 9. — Ulrich, 14th Ann. Rep. Geol. Surv. Minnesota, 1886, pp. 104, 113. — Wachsmuth and 
Springer, Rev. Pal., 3, sec. 2, 1886, p. 274. — Ringueberg, Ann. New York Acad. Sci., 4, 1889, p. 401. — 
Bather, Crinoidea of Gotland, 1893, p. 67; Treatise on Zool., 3, 1900, p. 147. — Jaekel, Phylogenie und 
System, 1918, p. 86. — Dcltacrinus, Bassler, Bibliogr. Index, Bull. 92, U. S. Nat Mus., 191S, pp. 156, 393. 
Arm-bearing rays 3. Calyx bilaterally symmetric, with stem in plane of 
anal tube. Median arm simple or branching, supported by compound 1 . ant. 
radial, the segments of which are usually separated. Lateral arms one on each 
side, supported by the large radials, branching- from unequal faces of the axil- 
lary primibrach and of successive diminishing axillaries curving around trans- 
versely toward the anal side, each axillary supporting at the shorter, inner face 
an axil-arm composed of successive series of 2 or 3 brachials, and bearing alter- 
nate ramules, and at the longer, outer face the next axillary; primibrachs of 
lateral arms usually 2. R. post, and r. ant. superradials fused to form a .subanal 
piece underlying anal jr, usually separated from the large radials by their respec- 
tive inferradials, or they may be eliminated. Basals reduced to 3 by fusion of 
1 . post, and 1 . ant. BB, the fused plate never or rarely entering the stem-facet. 
The foregoing characters apply also to the genus Halysiocrinus. 
R. post, and r. ant. inferradials usually not in contact, interposed between 
anal x or subanal piece and the large radials. The two segments of 1 . ant. com- 
pound radial exceptionally connected by short suture, but usually entirely sepa- 
rated as triangles by the large radials meeting between them. Fused left basal 
usually triangular with straight sides, and narrower than the hinge in the 
American species. Median arm usually simple. 
Genotype. Calceocrinus typus Ringueberg. 
Distribution. Silurian ; America, England, Gotland. 
The characters stated in the first paragraph are common to this and the next following 
genus. The axil-arm system characteristic of the two^ is a feature unknown in other crinoids ; 
in this by atrophy and fusion the two non-arm-bearing radials have become to a large extent 
eliminated, leaving the suprabasal portion of the calyx to consist, in addition to plates of the 
anal area, almost entirely of the two large simple radials, and the more or less interposed 1. ant. 
compound radial, upon the former of which the one-sided, thoroughly unique type of arm- 
structure has been established. This begins in the Silurian with numerous species in the 
Wenlockian of Sweden and England, and in the Niagaran of New York, Indiana, Missouri 
and Tennessee, extending through the Devonian into the Lower Carboniferous, where it 
culminates with the end of the family in the Keokuk and Warsaw beds of the IMississippi 
Valley. The extreme stage, in which the brachial series of the main arm are subordinated 
to the over developed outer ramules and thus hidden from view at the exterior, is confined to 
certain species of Calceocrinus, viz. : C. foerstei, C. bifurcatus and C. typus of the American 
rocks, and C. tenax, C. nitidus and C. inter pres of the European ; but never occurs, so far as 
known, in Halysiocrinus, in which some portion of the main arm is always more or less ex- 
