PISOCRINIDAE 
8l 
ZOPHOCRINUS S. A. Miller 
Plate 25 
Zophocrinus Miller, 17th Ann. Rep. Indiana Dep. Geol., 1892, p. 642 (adv. sheets, 1891, p. 32). — Weller, 
Bull. Chicago Acad. Sci., 4, 1900, p. 152, fig. 57.— Bather, Treatise on Zooh, pt. 3, 1900, p. 151, 
fig. 63. — Slocom, Field Columb. Mus., 2, Geol. Ser., 1908, p. 284, fig. 5. — Zittel-Eastman, Textb. Pal., 
2d ed., 1913, p. 158. — Bassler, Bibliogr. Index, 1915, p. I339- 
Monocyclic. Calyx elongate pyriform; BB 3, large, 2 ecjual and one larger ; 
RR 4, the one on the posterior side larger than the others, probably representing 
r. and 1 . post. RR fused. Tegmen solid, composed of 5 spade-shaped orals, inter- 
locking at the center and extending outward narrower to the periphery, where 
they connect with the radials; post, oral the largest, pushed in between the points 
of the other four; five groups of narrow plates resembling brachials, usually 
three in each group, closely united, two meeting behind the third, lie between 
the peripheral extensions of the orals; they spring from the radials and their 
distal ends are marked by fossae, indicating articular facets for slender arms. 
Surface smooth. Column-facet small. Specimens small, ranging from 5 mm. 
high to a maximum of 10 mm. 
Genotype. Zophocrinus howardi S. A. Miller. 
Distribution. Niagaran ; America ; not observed in Europe. 
Chiefly known from the type species, from which the characters of the genus are taken ; 
it occurs typically in the Laurel limestone, at St. Paul, Indiana, but has been found in Ten- 
nessee, and two species have been described from the Chicago area. 
This singular form is remarkable for the fact that whereas the dorsal cup is composed 
above the base of four radial elements, evidently formed by fusion of two from the primi- 
tive five, the tegmen is constructed strictly on the quinqueradiate plan, with 5 large orals 
meeting toward the center like those of Haplocrinns ; but unlike the latter connecting with 
the dorsal cup by extensions of a different shape, between which are groups of narrow plates 
supposed to be brachials. These groups, while connecting with the 4 large radials, do not 
seem to stand in any definite relation to them, as they do not, except occasionally, spring from 
their middle. Hence it would seem that the disturbance in radiation internally was greater 
than would be caused by a simple fusion of two radials, as in that case there should be a 
group of brachials from the middle of each of the three equal original radials, and two from 
the larger one. The anal opening is not always distinctly shown, but seems to lie closely 
alongside the peripheral extension of the posterior oral ; apparently this does not always coin- 
cide with the larger radial. 
Now it happens that the essential structures by which Zophocrinus differs so* markedly 
from other crinoids are found in the Devonian genus Tiaracrinus from the Eifel. This was 
described by Schultze in 1867 (Mon. Echin. Eifl., p. 226, pi. 13, fig. 8) from a single species, 
T. quadrifrons, but with a complete misconception of its characters. The tegmen with its 
border of narrow marginal plates he mistook for a stem segment, and figured his specimen 
upside down, so that the small cavity for the column-facet was conceived to be the tegminal 
opening where the calyx plates almost came together. This fact was noted by Zittel in 1879 ^ 
and has been further mentioned by Oehlert in connection with the description of a new 
species, T. soyei.^ 
1 Handb. Pal., i, p. 425. 
2 Bull. Geol. Soc. France, Ser. 3, 1882, p. 359. 
