ECHINODERMATA - KU ScholarWorks - University of Kansas

BLASTOID STUDIES 47
basais. Radials five, subquadrangular in side view, each
7.5 mm. long by 3.5 mm. wide, with short, wide, moderately
deep, flaring sinus 2.5 mm. long by 2.5 mm. wide,
with limbs projecting upward into low coronal processes;
radials overlapping deltoids.
Deltoids four, arrow-shaped, confined to summit, each
2 mm. long by 2.5 mm. wide, with aboral ends projecting
upward into low coronal processes, and four hydrospire
slits on each side of an ambulacrum crossing the radiodeltoid
suture to the adjacent radial limbs. On the anal
side there are three anal deltoids, a superdeltoid, subdeltoid,
and ?hypodeltoid (missing, but probably present in
living animal). The superdeltoid plate is hexagonal and
adjacent to the oral opening. The U-shaped subdeltoid
rests on the aboral inner surface of the superdeltoid and
has limbs that extend on either side of the anal opening
to the radial limbs. The radial limbs overlap the subdeltoid
limbs. Hydrospire slits are lacking on the anal side;
thus there are eight exposed hydrospire fields. The hypodeltoid
probably covered the aboral part of the anal opening
and fitted against the adjacent radial limbs.
Ambulacra five, linear, confined to summit, each 4
mm. long by 0.5 mm. wide, with lancet covered by side
plates, 42 side plates in 10 mm. length of an ambulacrum,
and side plates normally disposed. The primary and secondary
side plates are almost equal in size, each pentagonal,
with brachiolar pit and facets normally disposed.
The surfaces of the calyx plates are ornamented with fine
growth lines parallel to plate margins.
Remarks.—Comparison with other described species
clearly indicates that this species is distinct. The specimen
(holotype) is apparently mature and has a reduced number
of hydrospire slits as compared with other species of
Trionoblastus. It has not been possible to place this species
with others, especially with Trionoblastus gracilis,
which has eight slits on each side of an ambulacrum.
Occurrence.—Middle Devonian, Hamilton Group
(Cedar Valley Limestone), New Buffalo, Iowa.
Type.—Holotype, X-52, one specimen, A. H. Worthen
collection, old no. 10,398 of Illinois State Museum, now
in Department of Geology, University of Illinois, Urbana,
Illinois.
TRIONOBLASTUS ALATUS (Reimann)
Plate 5, figures 4-6; text-fig. 59
Codaster alatus REIMANN, 1935, P. 23, pl. 1, figs. 2-3.
Description.—The described specimen has six ambulacra,
and therefore is abnormal. Calyx calcitic, ohconical
in side view, hexagonal in top view (pentagonal
in normal specimens), 9.5 mm. long by 7 mm.
wide, with vault 2 mm. long, pelvis 7.5 mm. long, pelvic
angle 50 degrees, periphery at radial lips. The stem impression
is round, worn, 0.75 mm. in diameter, with
small round lumen. Basal circlet conical in side view,
rounded pentagonal in basal view, 4 mm. long by 4 mm.
wide, with three normally disposed basals. Radials six
(but normally five), each elongate hexagonal, 5.5 mm.
long by 3 mm. wide, with short, wide, moderately deep
sinus 2 mm. long by 2.5 mm. wide by 1 mm. deep. The
radial limbs on the anal side are truncated against the
subdeltoid limbs. Radials overlap deltoids.
Deltoids five (normally four), each strongly arrowshaped,
2.5 mm. long by 1 mm. wide, with approximately
five exposed hydrospire slits on each side of an
ambulacrum, extending across the adjacent radial limbs,
and each deltoid with a ventrally projected low coronal
process. On the anal side there are three anal deltoid
plates. The pentagonal superdeltoid is adjacent to the
oral opening and is bordered by the lancet plates on each
side. The thin horseshoe-shaped subdeltoid rests on the
aboral margin of the superdeltoid and is overlapped by
the radial limbs. It is assumed that the large anal opening
between the radial limbs and subdeltoid limbs was
FIGURES 57-67. Species of Trionoblastus FAY, n. gen., Middle Devonian, North America.
57, 58. T. subtruncatus (HALL), Cedar Valley Limestone,
New Buffalo, Iowa (Univ. Illinois, holotype, no. X-52);
57, morphological features of anal area and part of "BC"
interambulacrum, X15; 58, part of "D" ambulacrum
showing main and outer side plates, X45. 59. T.
alatus (REImANN), Traverse Group, Alpena, Mich. (Univ.
Michigan, no. 30,736); part of "E" ambulacrum, showing
main and inner side plates, X90. 60 63, T. canadensis
(BILLINGS), Hungry Hollow Formation, Thedford, Ontario
(G.S. Canada, 3,664; Buffalo Soc. Nat. Sci.,
E11,760, E21,098); 60, "BC" interambulacrum, showing
morphological features (no. E11,760), X15; 61, stem
(E21,098), X45; 62, part of "A" ambulacrum showing
main and outer side plates (no. E11,760), x90; 63, part
of "C" ambulacrum, showing main and outer side plates
(no. 3,664), X75. 64 66. T. gracilis (W Acnsmuni),
Partridge Point Formation, Partridge Point, Mich. (Buffalo
Soc. Nat. Sci., no. E21,142); 64, summit area showing
morphological features of "CD" (anal) and "BC"
interainbulacra, X15; 65, part of "C" ambulacrum, showing
main and outer side plates, X45; 66, part of "E" ambulacrum,
showing main and outer side plates drawn
from polished tangential section, X45. 67. T. pyramidatus
(SHumARD), Columbus Limestone, Columbus,
Ohio (Buffalo Soc. Nat. Sci., no. E21,071); part of "A"
ambulacrum, showing main and outer side plates, X45.
[Explanation.—An, anal opening; Bf, brachiolar facet;
Bp, brachiolar pit; "C," amb.; "D," amb.; D, deltoid; Db,
deltoid body; Dl, deltoid lip; HD, hypodeltoid; Hs, hydrospire;
Lu, lumen; 0, oral opening; OSp, outer side plate;
RI, radial limb; Sp, main side plate; Ss, spiracular slit;
Su, superdeltoid; Sub, subdeltoid; Z, azygous basal.]