ECHINODERMATA - KU ScholarWorks - University of Kansas

BLASTOID STUDIES 77
convex, 4 mm. wide, with three normally disposed basais,
each with a prominent central rounded ridge. Radials
five, elongate subquadrangular, recurved below, each 5.5
mm. long by 4 mm. wide, with long, wide, shallow sinus
5 mm. long by 1.5 mm. wide; radials overlapping deltoids.
Deltoids four, short, lancet-shaped, barely visible in
side view, each 1.75 mm. long by 1.5 mm. wide, the
adorai tip of each notched by two large elliptical spiracles
with a flat, wide median septum between. Each deltoid
lip has approximately 14 prominent cover-plate sockets
on its oral and lancet margins. On the anal side there
are four deltoid plates, a superdeltoid, two cryptodeltoids,
and a hypodeltoid. The V-shaped superdeltoid is adjacent
to the oral opening and together with the other four
deltoid lips helps to surround the oral opening. The two
bluntly lenticular cryptodeltoids, adjacent to the side
plates and below the hypodeltoid, separate the anal opening
internally from the anal spiracles. Internally the
cryptodeltoids are overlapped by the adjacent radial limbs.
The pentagonal hypodeltoid abuts against the radial limbs
and covers the aboral end of the anal opening and ad-.
jacent hyprospire canals. Thus nine orifices surround the
oral opening—eight spiracles and the anispiracle. Three
hydrospire folds are present on each side of an ambulacrum,
ending admedially in a thick hydrospire plate.
Approximately five hydrospire pores to each side plate
are seen, three almost hidden being adjacent to the side
plate, and two others between but slightly abmedial to
the first three, visible, and slightly outward from them.
The latter two pores appear to branch from the former
three, forming a more or less connected system. Pores
are absent along the deltoid margins.
Ambulacra five, broadly linear, recurved below, each
7 mm. long by 1.5 mm. wide, with lancet covered by side
plates from mid-height downward but fully exposed at
adorai end. Side plates are normally disposed, with 26 in
a space of 10 mm. along an ambulacrum; a triangular
outer side plate occurs on the bevelled abmedial-adoral
corner of each primary side plate, with six main coverplate
sockets to each side plate along the main food
groove. The surfaces of the calyx plates are ornamented
by fine growth striae parallel to plate margins, except on
the deltoids. The deltoids have coarse granules arranged
along growth lines.
Occurrence. — Lower Carboniferous, Tournaisian,
Tournai, Belgium.
Types.—Topotypes?, 5,196, two specimens, Krantz
collection, one specimen fragmentary, one almost perfect;
19,083, four specimens labelled Orophocrinus puzos,
Gurley collection, University of Chicago. The above description
is mainly based on specimen 5,196. Topotypes?,
536, 23 specimens, old no. 2,326, deKoninck collection,
Harvard Museum of Comparative Zoology, Cambridge,
Mass. Topotypes?, S3,775, 24 specimens, Springer collection,
from Lower Carboniferous shale of the "Mountain
Limestone" of Tournai, Belgium; sent by Dr. A.
Krantz of Bonn, Germany, to U. S. National Museum,
Washington.
Genus METABLASTUS Etheridge & Carpenter,
1886
Type-species, by original designation.—Pentremites lineatus SHU-
MARD, 1858.
Generic diagnosis.—Spiraculate blastoids with five
paired spiracles, or four paired spiracles in addition to
a paired anispiracle, with superdeltoid, two cryptodeltoids,
and a hypodeltoid plate on the anal side,
lancet covered by side plates, one pore between adjacent
side plates along deltoid and radial margins,
radials overlapping deltoids, four or five hydrospire
folds on each side of an ambulacrum, radial plates
thin, pelvis long, conical, deltoids not visible in side
view but large hypodeltoid visible in side view; calyx
form conical, with aborally directed ambulacra. Mississippian,
Illinois, Iowa, Indiana, Missouri, Kentucky.
Remarks.—The genus Metablastus was probably
derived from a form similar to Troosticrinus in which
the pelvis became elongate and ambulacra moved
downward. The type species occurs in the Burlington
Limestone (Osagian) and is different from the Keokuk
(Osagian), Warsaw, and Salem (Meramecian)
species. The latter group have flaring radial bodies,
whereas the type does not. The latter group probably
represents intermediate stages between Metablastus
and Tricoelocrinus but are here classed with Metablastzts
because the radial plates of this group are thin
and there are four or five hydrospire folds on each side
EXPLANATION OF PLATE 24
FIGURE PAGE
1-2,6. Devonoblastus leda (HALL), syntypes, 451 (figs. 1,6),
452 (fig. 2), New York State Mus., Albany; Middle Devonian,
Hamilton Shale, western New York; 1, aboral view
(X8.4 ); 2, ambulacrum showing side plates (X56.5);
6, side view of calyx (X6.4) 62
3-5. Devonoblastus whiteavesi R El M N N, plesiotype, 3,661,
Geol. Survey Canada, figured by WHITEAVES (1889, pl.
14, figs. 3a-d,f); Middle Devonian, Hamilton Group, near
Thedford, Ontario oral, "D" ambulacral aboral views of
nearly perfect specimens (all X3.3) 62