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100 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS
Type.—Holotype, 1,290, one specimen, C. C. Branson
collection, University of Missouri, Columbia.
Genus PTYCHOBLASTUS Fay, 1960
Type-species, by original designation.—Ptychoblastus pustulosus FAY,
1960.
Generic diagnosis.—Spiraculate blastoids with nine
spiracles, or eight spiracles and anispiracle located between
an epideltoid and hypodeltoid, radials abutting
against deltoids, hydrospire plate present, two pores
to each side plate and along deltoid and radial margins,
one hydrospire fold on each side of an ambulacrum,
lancet covered at aboral end but gradually exposed
to one-third of its width near the adorai end;
shape of calyx ellipsoidal. Mississippian, Missouri.
Remarks.—The genus Ptychoblastus was probably
derived from Poroblastus by infolding of the poral
canals along the deltoid margins to form two pores to
each side plate, and downward migration of the deltoid
plates so that they abut against the radials.
PTYCHOBLASTUS PUSTULOSUS Fay
Plate 42, figures 4-7, 9-10
Ptychoblastus pustulosus FAY, 1960, pp. 1198-1201, text-fig. 1.
Description.—A detailed description is given in the
above article and is not here repeated. Of importance is
the presence of two pores to each side plate along the
deltoid margins and radials abutting against the deltoids.
Occurrence.—Upper Mississippian, Warsaw Limestone,
12 feet below the top, SW1/4 NW1/4 SW1/4 sec. 9,
T. 44 N., R. 5 E., just below level of St. Louis & San
Francisco RR tracks, Keyes Summit, St. Louis County,
Missouri.
Types.—Holotype, 3,643; paratypes, 3,644 (a thinsection),
and 3,645 (six specimens and one thin-section
with fragment), Geology Department, University of
Oklahoma, Norman.
Genus SCHIZOBLASTUS Etheridge & Carpenter,
1882
Pype-species, by subsequent designation (ETHERIDGE & CARPENTER,
1886).—Pentremites sayi SittimARD, 1855.
Generic diagnosis.—Spiraculate blastoids with 11
openings around the mouth, consisting of ten spiracles
and separate anus, which is located between an epideltoid
and hypodeltoid, lancet exposed along main food
groove, one pore between side plates along deltoid and
radial margins, deltoids moderately long, deltoids overlapping
radials, two hydrospire folds on each side of
an ambulacrum; form of calyx ellipsoidal. Mississippian,
Iowa, Missouri.
Remarks.—The genus Schizoblastus was probably
derived from a genus approaching Schizotremites, in
which the deltoid septa moved out to form ten
spiracles with anus separate, cryptodeltoids fused with
superdeltoid to form an epideltoid, and lancet moved
out and down while the hydrospires atrophied to two
folds on each side of an ambulacrum.
SCHIZOBLASTUS SAYI (Shumard)
Plate 46, figures 1-2; text-figs. 207-208
Pentremites sayi SHUMARD, 1855, p. 185, pl. B, figs. la-d.
Cri broblastus sayi HAMBACH, 1903, p. 42, pl. 5, fig. 14.
Schizoblastus sayi var. sayi CLINE, 1936, p. 269, pl. 44, figs. 17-22.
Description.—The holotype is fragmentary. Calyx
calcitic, 12 mm. long by 16 mm. wide, crushed on one
side, in limestone matrix. Base slightly concave. Shape
of calyx widely elliptical in side view. Deltoids overlap
radials and extend below the periphery for about threefourths
the length of the specimen. Spiracles apparently
ten, separate from anus, with anus between an epideltoid
and hypodeltoid plate. Ambulacra five, linear, each
19-20 mm. long by 1.5 mm. wide, recurved below, with
lancet exposed along the middle one-fifth of its width
along the main food groove, and 32 side plates in a space
of 10 mm. along an ambulacrum. The anal opening is
covered on the aboral side by a low adorai projection of
the hypodeltoid plate. Each deltoid plate has three longitudinal
ridges extending toward the adorai tip, one in the
mid-line of the plate and two marginal ones. The surfaces
of the calyx plates are ornamented by fine growth
lines subparallel to plate margins, with a tendency toward
granulation.
EXPLANATION OF PLATE 33
FIGURE PAGE
1-9. Placoblastus angularis (LvoN), plesiotypes, 13,890 (figs.
1-6), Gurley coll., Univ. Chicago, Middle Devonian, Hamilton
Group, Charlestown, Ind., 19,052 (figs. 7-9), Falls
of the Ohio, near Jeffersonville, Ind.; 1-3, oral, "D" ambulacral,
and aboral views of average specimen, (X2.9);
4-6, oral, "D" ambulacral, and aboral views of a gerontic
specimen (X2.2); 7-9, oral, "D" ambulacral, aboral views
of four-sided specimen in which the "A" ambulacrum
failed to develop, thus with only four radials and four
deltoids (X7) 95