ECHINODERMATA - KU ScholarWorks - University of Kansas

92 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS
on the lancet plate. The surfaces of the calyx plates are
ornamented by coarse raised ridges subparallel to plate
margins, each ridge with low, aligned, round pustules.
Occurrence.—Lower Carboniferous, Uebergangskalke
or transition limestone, Etroeungtian, Cromford bei
Ratingen, Germany.
Types.—Topotypes, 151, four specimens, deKoninck
collection, old no. 2,331, one specimen of which was used
for the above description; 316, four specimens, Bronn or
Brown collection, old no. 2,351, Harvard Museum of
Comparative Zoology, Cambridge, Mass.
Genus PLACOBLASTUS Fay, n. gen.
Type-species, by original designation (herein).—Elaeacrinus obovatus
BARRIS, 1883.
Generic diagnosis.—Spiraculate blastoids with 11
openings around oral aperture, consisting of ten
spiracles and anus separate, six or seven large oral
plates, one of which may be a superdeltoid exposed
between the adorai ends of the two cryptodeltoids,
with a hypodeltoid between two exposed cryptodeltoids,
at least one anal oral between adoral tips of
the two cryptodeltoids, lancet covered by side plates,
an inner side plate present, one pore between side
plates along deltoid and radial margins, deltoids long,
overlapping radials, with two hydrospire folds on
each side of an ambulacrum bearing a long hydrospire
canal; form of calyx elongate elliptical. Devonian,
Iowa, Michigan, New York, Indiana, Ohio.
Rem arks.—The genus Placoblastus was probably
derived from Elaeacrinus by reduction in the number
of the oral plates and elongation of the hydrospire
canals.
PLACOBLASTUS OBOVATUS (Barris)
Plate 31, figures 1-9; text-figs. 193-196
Elaeacrinus obovatus BARRIS, 1883, P. 358, fig. 3; 1885-86, p. 88,
text-fig. 3, pl. I, figs. 1 -2.
Nucleocrinus obovatus CLELAND, 1911, p. 43, pl. 3, fig. 2.
Nucleocrinus obovatus THOMAS, 1924, p. 423, pl. 36, figs. 1, 6-9,
16-17, text-fig. 65.
Description.—Calyx calcitic, 47.5 mm. long by 25 mm.
wide, deformed, and another specimen is 48 mm. long
by 30 mm. wide, undeformed. The former specimen is
elongate, oval in side view, with deeply concave base and
periphery above mid-height. Basal circlet small, within
basal concavity, approximately 3 mm. in diameter. Radials
L?a
FIGURE 193. Placoblastus obovatus (BARRIS), Middle
Devonian, Thunder Bay Limestone, near Alpena, Michigan
(Buffalo Soc. Nat. Sci., no. E21,115); summit area,
X11.7. [Explanation.—An, anal opening; CR, cryptodeltoid;
D, deltoid; HD, hypodeltoid; L, lancet; 0, oral
plate; S, spiracle; Su, superdeltoid.]
EXPLANATION OF PLATE 29
FIGURE PAGE
1-3,7-8. Nucleocrinus meloniformis (BARRis), plesiotype,
E21,120, Charles Southworth coll., Buffalo Soc. Nat. Sci.;
Middle Devonian, Hungry Hollow Formation (coral zone
of Widder beds), tile yard, Thedford and Hungry Hill,
Arkona, Ontario; 1-3, oral, "D" ambulacral, aboral views
( X7.1); 7, oral view of specimen shown in fig. 1, oral
plates removed to show small superdeltoid hidden adjacent
to oral opening ( X17.8); 8, oral view of another specimen
with oral plates in place, showing adorai tips of
cryptodeltoids abutting aaginst one large oral plate on anal
side, four other orals covering mouth (X15) 86
4-6,9. Nucleocrinus elegans CONRAD, topotype, 19,049, Gurley
coll., Univ. Chicago, one of two specimens, other probably
belonging to Placoblastus lucina (HALL); Middle Devonian,
Hamilton Group, Moscow, N.Y.; 4-6, oral, "D" ambulacral,
aboral views ( X4.4); 9, oral view showing five
large oral plates, that on anal side abutting against adorai
tips of cryptodeltoids ( X2.6) 84