ECHINODERMATA - KU ScholarWorks - University of Kansas

BLASTOID STUDIES 49
Deltoids four, arrow-shaped, with moderately high
coronal processes, and seven or eight exposed hydrospire
slits on each side of an ambulacrum, extending to adjacent
radial limbs. On the anal side there are three deltoid
plates. The hexagonal superdeltoid is adjacent to the
oral opening and the horseshoe-shaped subdeltoid rests on
the inner aboral surface of the superdeltoid. The subdeltoid
limbs curve around the sides of the anal opening and
meet the truncated radial limbs. It is assumed that a
hypodeltoid plate was present on the aboral side of the
anal opening, where a facet is present. Hydrospire slits
are lacking on anal side; thus there are eight exposed
hydrospire fields.
Ambulacra five, linear, each 3.5 mm. long by 0.5 mm.
wide, with approximately 50 side plates in 10 mm. The
primary and secondary side plates are pentagonal and
almost equal in size, with four or five cover-plate sockets
to each side plate along the main food groove. The surfaces
of the calyx plates are ornamented with fine growth
lines parallel to plate margins.
Occurrence.—Middle Devonian, Partridge Point Formation,
Partridge Point, Michigan.
Types.—Plesiotypes, E21,142, 12 specimens, Reimann
collection, Buffalo Society of Natural Sciences, Buffalo,
New York.
TRIONOBLASTUS PYRAMIDATUS (Shumard)
Plate 4, figures 7-9; Plate 12, figure 8; text-figs. 67, 68
Codaster pyramidatus SHUMARD, 1858, p. 238, pl. 9, figs. la-c.
Description.—Calyx silicified, obconical in side view,
pentagonal in oral view, 12 mm. long by 8 mm. wide,
with vault 2 mm. long, pelvis 10 mm. long, pelvic angle
45 degrees, and periphery at radial lips well above midheight.
Basal circlet rounded in aboral view, broadly triangular
near area of stem attachment, 3.5 mm. long by
4 mm. wide, with three normally disposed basals. Stem
round, 1 mm. in diameter, with small round lumen.
Radials five, each broadly pentagonal in side view, 8 mm.
long by 4 mm. wide, with broad flat sinus 3 mm. long
by 3.5 mm. wide, and low limbs. The interradial sutures
are in depressed areas flanked by a double or triple row
of parallel ridges on either side; radials overlapping deltoids.
Deltoids four, arrow-shaped, with low crests, and seven
hydrospire slits on each side of an ambulacrum, extending
to adjacent radial limbs. On the anal side there
are three deltoids. The arrow-shaped superdeltoid is
adjacent to the oral opening. The subdeltoid is horseshoeshaped,
adjacent to the aboral surface of the superdeltoid,
with limbs that extend on both sides of the anal opening
and meet the adjacent radial limbs which overlap the
subdeltoid limbs. It is assumed that a small hypodeltoid
plate covered the aboral part of the anal opening and
abutted against the radial limbs. Hydrospire slits are absent
on anal side; therefore there are eight hydrospire
fields.
Ambulacra five, linear, each 4.5 mm. long by 1 mm.
wide, with lancet covered by side plates, and 50 side
plates in 10 mm. The side plates appear to be normally
disposed. The surfaces of the calyx plates appear to be
ornamented with fine growth lines parallel to plate margins.
Remarks.—The flat summit and ridges parallel to the
interradial sutures serve to characterize this species. The
variously described species of Trionoblastus may readily
be distinguished by the number of hydrospire slits in each
field, and the relative height of the deltoid crests.
Occurrence.—Middle Devonian, Onondaga (Columbus)
Limestone, Columbus, Ohio.
Types.—Plesiotypes, 37,759, eight specimens, U. S.
National Museum, Washington; E21,071, seven specimens
used for the above description, Buffalo Society of
Natural Sciences, Buffalo, New York.
Order SPIRACULATA Jaekel, 1918
Blastoids with hidden hydrospire slits that open
into hydrospire canals, haying definite spiracles and
hydrospire pores. Silurian -Permian, North America,
Europe, Timor, Australia, Asia, North Africa.
EXPLANATION OF PLATE 12
FIGURE PAGE
1-7,9. Codaster acutus M'Cov, plesiotype (figs. 1-3), S3,218,
Springer coll., U.S. Natl. Mus., Lower Carboniferous limestone,
Lancashire, England; plesiotypes (figs. 4-7,9), 367,
Harvard Mus. Comp. Zoology, Lower Carboniferous limestone,
Malham, Yorkshire, England; 1-3, oral, "D" ambulacral,
aboral views (all X3.7); 4-6, oral, "D" ambulacral,
aboral views (all X4.6); 7, enlarged view of "E"
ambulacrum of another specimen ( X16); 9, thin sec. of
anal area of a third specimen, showing epideltoid against
radial limbs (anal area in white) ( X16) 23
8. Trionoblastus pyramidatus (SHumARD), plesiotype, 37,759,
U.S. Natl. Mus.; Devonian, Onondaga Limestone, Columbus,
Ohio; oral view, for comparison with Codaster, showing
subdeltoid plate on adorai side of anal opening, adjacent
to superdeltoid plate, with distinct suture between
the two plates ( 7) 49