ECHINODERMATA - KU ScholarWorks - University of Kansas

24 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS
CONOSCHISMA LAEVIUSCULUM (Rowley)
Plate 14, figures 9, 11-12; text-fig. 10, 11
Codaster (Cryptoschisma?) laeviusculus ROWLEY, 1900, p. 65, pl. 2,
figs. 51-55; p. 271, pl. 5, fig. 74.
Description.—Calyx of topotype consisting of an internal
mold, silicified, obconical in side view, rounded
pentagonal in top view, 12 mm. long by 7 mm. wide,
with periphery near mid-height at radial lips, vault 5 mm.
long, pelvis 7 mm. long, and pelvic angle on basal circlet
60 degrees and on radial bodies 35 degrees. Stem impression
not observed. Basal circlet conical in side view, pentagonal
in basal view, 4.5 mm. long by 5 mm. wide, with
three normally disposed basais. Radials five, elongate
hexagonal, each 7 mm. long by 4 mm. wide, with short,
wide, shallow sinus 3 mm. long by 3 mm. wide; radials
overlapping deltoids.
Deltoids four, lanceolate, each 2.5 mm. long by 2 mm.
wide, not seen in side view, with approximately seven
hydrospire slits on each side of an ambulacrum extending
to adjacent radial limbs. On the anal side approximately
four hydrospire slits occur on each side of the
elongate anal opening, and judging from the sutural
markings two deltoid plates seem to be present on the
anal side—a large horseshoe-shaped epideltoid with hydrospire
slits, and a small pentagonal hypodeltoid that
covered the aboral end of the anal opening. Thus ten
hydrospire fields and two anal deltoids are recognized.
Ambulacra five, narrow, linear, with small narrow
lancet plate 3.5 mm. long by 0.25 mm. wide, completely
covered by side plates. The surfaces of the calyx plates
appear to be ornamented with fine growth striae parallel
to the plate margins.
Remarks.—The genus Conoschisma probably was de-
FIGURES 10, 11. Conoschisma laeviusculum (RowLEY),
Lower Mississippian, Missouri (Univ. Chicago, 29,904).
10. Plates adjacent to anal opening, X15. 11.
Deltoid of "BC" interambulacrum and adjoining elements,
X15. [Explanation.—An, anal opening; "B," amb.;
"C," amb.; D, deltoid; ED, epideltoid; HD, hypodeltoid;
Hs, hydrospire slit; L, lancet; R, radial; RI, radial limb.]
[Preface to Explanation of Plates. Unless otherwise noted, the
oral views are oriented with the anal opening toward the bottom
of the page, the side views with the "D" ambulacrum toward the
observer, and the aboral views with the "A" ambulacrum toward
the bottom of the page and the azygous basal (Z) in the lower
right ("AB") position. In oral view, the ambulacra are lettered
"A" through "E" proceeding in a clockwise direction with "A"
EXPLANATION OF PLATE 1
FIGURE
PAGE
1-3. Decaschima pulchellum (MILLER & DYER), topotype,
2,810, Washburn coll., Univ. Chicago; Silurian, Waldron
Shale, Waldron, Ind.; oral, "D" ambulacral, aboral views
(all X6.7) 27
4-6. Deltoschisrna archiaci (ETHERIDGE & CARPENTER), topotype,
13,876, Gurley coll., Univ. Chicago; Lower Devonambulacrum
at the top. In side view, "C" ambulacrum is at right,
"D" ambulacrum is in the middle, and "E" ambulacrum is at left,
with the oral opening toward top of the page. In aboral view, the
ambulacra are lettered "A" through "E" proceeding in a counterclockwise
direction with "A" ambulacrum toward the bottom of
the page.]
ian, Calizas de Ferrofies, from Ferrofies, Asturias, Spain;
oral, "D" ambulacral, aboral views, (all X7) 29
7-10 Decaschisma pentalobus (HALL), topotype, 2,554, Washburn
coll., Univ. Chicago; Silurian, Waldron Shale, Waldron,
Ind.; oral, aboral, "D" ambulacral, anal views (7-9,
X3.8; 10, X8.8) 27