ECHINODERMATA - KU ScholarWorks - University of Kansas

BLASTOID STUDIES 21
Order FISSICULATA Jacket, 1918
Blastoids with exposed hydrospire slits or spiracular
slits. Silurian-Permian. North America, Europe,
Asia, Timor, Australia, North Africa, South America.
Genus ASTROCRINUS Morris, 1843
[.-..4ilracrinues AUSTIN & AUSTIN, 1842 (nom. nud.) and 1843 (invalid original
spelling); eturocriniter AUSTIN & AUSTIN, 1843 (non CONRAD, 1841, nec
MATHER, 1843, nec DEKONINCK, 1854); Zygocrinus BROWN, 1848]
Type-species, by original designation (monotypy). AstrocTinus tetragonus
MORRIS, 1843.
Generic diagnosis.—Fissiculate blastoids with eight
spiracular slits along margins of ambulacra; epideltoid
and possible hypodeltoid, slits lacking on anal
side, with short wide "D" (left posterior) ambulacrum;
one basal plate, and star-shaped in top view,
with lancet covered by side plates; calyx spinose.
Lower Carboniferous, Scotland, England.
Remarks.—The genus Astrocrinus appears to have
been derived from a form similar to Pentremitidea in
which the interambulacral areas have moved outwards,
the (D) ambulacrum becoming foreshortened, the
hypodeltoid atrophied or reduced in size, and the
basais fused.
ASTROCRINUS BENNIEI (Etheridge)
Plate 17, figures 1-3, 7-9; text-figs. 1-3
Astrocrinites benniei ETHERIDGE, 1878, p. 103.
Astrocrinus benniei ETHERIDGE & CARPENTER, 1886, p. 301, pl. 19,
fig. I; pl. 20, fig. 3-20.
Zygocrinus benniei BATHER, 1899, p. 69; 1900, p. 91, text-fig. 14.
NVANNER, 1932, p. 456-458, text-fig. 1-4; 1933, p.
496, text-fig. 36.
Description.—The studied specimens, which are
crushed and damaged on the anal side, range in size
from 2.5 to 4.5 mm. Of importance here is the fact that
the lancet is covered by the side plates, and the outer
side plates rest upon the abmedial-adoral bevelled corners
of the primary side plates, with a large brachiolar facet
on each.
Occurrence.—From the shale above the no. 2 limestone
of the Lower Carboniferous Limestone group, at
Carlops Quarry, Peebleshire, Scotland.
Types.—Plesiotypes, 362, six specimens, Harvard
Museum of Comparative Zoiilogy, Cambridge, Mass.
Genus BRACHYSCHISMA Reitnann, 1945
Type-species, by original designation.—Codaster corrugatus RE1-
MANN, 1935.
Generic Diagnosis.—Fissiculata with nine exposed
hydrospire fields, superdeltoid, subdeltoid, hypodeltoid,
lancet covered by side plates, and conical in
side view. Devonian, New York.
FIGURES 1-3. Astrocrinus benniei ( ETHERIDGE), Lower
Carboniferous, Scotland (Harvard Mus. Comp. Zoology,
362). 1. Oral view of "AB" deltoid ( X15).
2. "A" ambulacrum, X90. Oral view of spine on
"BC" deltoid, X90. [Explanation.—Bf. brachiolar facet;
Bp, brachiolar pit; D, deltoid; L, lancet; OSp, outer side
plate; Sp, main side plate; Ss, spiracular slit.]
BRACHYSCHISMA CORRUGATUM (Reimann)
Plate 6, figures 1-9; text-figs. 4-7
Codaster corrugatus REIMANN, 1935, p. 25, pl. 4, figs. 1-2.
Description.—The description is taken mainly from
features seen in specimen E21,134. Calyx broadly conical
in side view, stellate in oral view, 16 mm. long by 9 mm.
wide; vault 6 mm. long, pelvis 10 mm. long, with pelvic
angle on basals 50 degrees and on radial bodies 95 degrees.
Basal circlet broadly pentagonal in outline, 6 mm.
long by 7 mm. wide; with round stem impression about
1.5 mm. in diameter in center. Basals three, large, normally
disposed, with coarse growth lines parallel to margins.
Radials five, each 10 mm. long by 6 mm. wide, with
wide sinus 5 mm. long by 6 mm. wide, and coarse growth
lines parallel to margins; radials overlapping deltoids.
Deltoids four, bluntly arrow-shaped, confined to summit,
with seven or more hydrospire slits barely notching
the margin of each next to radiodeltoid suture. Three
deltoids on the anal side, epideltoid adjacent to the oral
opening and homologous with deltoid lips of the other
four deltoids; subdeltoid on the adoral side of the anal
opening, horseshoe-shaped and notched on the right side
("C" ambulacrum) by five hydrospire slits which extend
to the radial limb. On the left side of the anal opening,
the subdeltoid limb appears to be notched with two incipient
hydrospire slits which are not seen to penetrate
the radial limb and subdeltoid limb at depth. The thick
quadrangular hypodeltoid is aboral to the anal opening
and rests on the radial limbs and aboral ends of the subdeltoid
limbs. Thus, there are nine hydrospire fi elds and
three anal deltoids. The hydrospire slits are elongate on
each radial limb, within the sinus of each ambulacrum.
The oral opening is surrounded by the four deltoid lips
and superdeltoid.
The ambulacra are linear, 8 mm. long by 1.5 mm.
wide, with lancet covered by side plates, and 30 side
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