ECHINODERMATA - KU ScholarWorks - University of Kansas

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BLASTOID STUDIES 109
as result of outward migration of the deltoid septa
and fusion of the superdeltoid and cryptodeltoids into
an epideltoid. Thus, Schizoblastits may have been derived.
Acentrotremites could have been formed from
Schizoblastus by atrophy of pores along the deltoids,
with consequent downward migration of the ten
spiracles and infolding of the radial margins to form
a hydrospire plate and numerous pores, with fusion
of the three basals into one. Deltoblastus probably
came from Schizoblastus by outward migration of the
lancet plate and retrogressive overlap of the deltoids
by the radials.
The Granatocrinidae FAY, n. fam., which contains
blastoids having nine spiracles, exhibits diverse
trends. The various genera probably came from a form
related to Schizotremites, by reduction of the number
of hydrospire folds to three, with retention of simple
pores along deltoid and radial margins (Lophoblastus),
or with loss of pores along deltoids and development
of five pores to each side plate along radial
margins (Mesoblastus). The remaining genera (except
Calycoblastus) can be derived from Lophoblasttts.
One trend is toward Carpenteroblasttts, in which the
number of hydrospire folds is reduced to two. The
trend toward Tanaoblastus involves reduction of bydrospires
to two, loss of pores along deltoid margins,
formation of a hydrospire plate, and occurrence of
two pores to each side plate as a result of infolding
of the ambulacral margins of the radials. The
trend toward Poroblastus from Lophoblastus is
marked by reduction of the hydrospire folds from
three to one, retention of simple pores along the deltoid
margins, but formation of a hydrospire plate and
formation of multiple pores to each side plate along
the radial margins. The trends from Car penteroblas
are toward reduction in number of folds to a
single hydrospire fold on each side of an ambulacrum,
with downward movement of deltoids over the radials
(Monoschizoblastus), or toward formation of deltoid
coronal processes and a concave base (Cribroblastus),
from which Heteroblastus could have been derived
by downward movement of deltoids over the radials.
Cal ycoblastus may have been produced from Schizotremites
by atrophy or suppression of the hypodeltoid.
Tanaoblastus probably gave rise to Cryptoblastus as
consequence of wedge-shaped overlap of radials on the
deltoids, and to Monadoblastus by atrophy of the bydrospire
folds to one on each side of an ambulacrum,
accompanied by development of a concave base. The
trends from Poroblastus are toward formation of multiple
pores along deltoid margins, with increase in
size (Granatocrintts), or with retention of small size
and abutment of radials against deltoids (Ptychoblastus).
Extensive restudy of many old-named blastoid
species is needed. These are not considered in this
paper because types or other specimens are unavailable
for study, or time did not permit. For instance, the
form known as Orbitremites malaianus from Permian
beds of the Basleo region in Timor in all probability
is a species of a new genus if demonstrated to have a
simple epideltoid on the anal side instead of a superdeltoid
and two cryptodeltoids; Tricoelocrintts? belfordi,
of the Permian Fenestella shale of New South
Wales, and T.? car penteri, of the Permian Gympie
beds of Queensland, probably also belong to a new
genus if shown to possess an cpideltoid instead of a
superdeltoid and two cryptodeltoids on the anal side;
Tricoelocrinus? leai, of the Devonian Tor Bay Limestone
of Devonshire, England, is probably misplaced,
actually belonging to some other genus; various species
referred to Codaster are judged likely to belong to
other genera (e.g., C. blairi, C. curtus, C. gracillirnus,
C. grandis, C. gratiosus, C. hindei, C. lorae, and C.
superbus); Mesoblasttts attstralis, of the Permian
Gympie beds of Queensland, probably belongs to some
EXPLANATION OF PLATE 38
FIGURE PAGE
1-3,5. Tanaoblastus concinnulus (Rawl= & HARE), holotype,
one of three specimens (figs. 1-3), paratype, polished section
(fig. 5), Robert R. Rowley coll., Univ. Illinois; Lower
Mississippian, base of Lower Burlington Limestone, Louisiana,
Mo.; 1-3, oral, "D" ambulacral, aboral views of hobotype
( X7): 5, oral view of polished section showing hydrospires
( X 8) 103
4. Cryptoblastus shumardi (MEEK & WORTHEN), topotype,
S3,765, Springer coll., U.S. Natl. Mus.; Lower Mississippian,
Lower Burlington Limestone, Burlington, Iowa;
crushed specimen showing form of brachioles attached to
calyx (X2.8) 61
6-9. Cryptoblastus fnelo (OwEN & SHUMARD)-6. Unlabelled
specimen, Philadelphia Acad. Sci. Mus.; ?Mississippian,
?locality; view showing cryptodeltoid (dark calcite) adjacent
to lancet plate on right with hypodeltoid partly
removed, anal opening black (X14.6). 7-9. Neotype
(new holotype), S4,959, Springer coll., U.S. Natl. Mus.;
Lower Mississippian, Lower Burlington Limestone, Burlington,
Iowa; oral, "D" ambulacral, aboral views (all
X 4.4) 61