ECHINODERMATA - KU ScholarWorks - University of Kansas

50 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS
68
FIGURE 68. Trionoblastus pyramidatus (SHumARD),
Columbus Limestone, Columbus, Ohio (Buffalo Soc. Nat.
Sci., no. E21,071); summit area showing morphological
features of "CD" (anal) and "BC" interambulacra, X11.
[Explanation.—An, anal opening; "C," amb.; "D," amb.;
D, deltoid; HD, hypodeltoid; Hs, hydrospire slit; 0, oral
opening; R1, radial limb; Su, superdeltoid; Sub, subdeltoid.]
Genus AMBOLOSTOMA Peck, 1930
Type-species, by original designation.—Ambolostoma baileyi PECK,
1930.
Generic diagnosis.—Spiraculate blastoids with five
spiracles, including anispiracle in one anal deltoid
plate, with five large oral plates covering summit,
lancet completely exposed, with one large pore between
side plates along deltoid and radial margins,
three hydrospire folds on each side of an ambulacrum,
and calyx shape elliptical in side view. Mississippian,
Utah, Alberta.
Remarks.—The genus Ambolostoma was probably
derived from Pentremites by enlarged growth of oral
plates into five large orals.
AMBOLOSTOMA BAILEYI Peck
Plate 53, figures 1-6; text-figs. 69-73
Ambolostoma baileyi PECK, 1930, p. 104, pl. 14, figs. 9-13.
Pentremites grandis WARREN, 1927, p. 48, pl. 3, fig. 8.
Pentremites perelongatus WARREN, 1927, p. 48, pl. 3, fig. 9.
Description.—The above-cited nominal species are
represented by imperfectly preserved specimens but all
appear to be conspecific. The best specimens are the syntypes
of Ambolostoma baileyi, adequately described by
PECK. The largest specimen is 64 mm. long by 35 mm.
wide, vault 52 mm. long, pelvis 12 mm. long. The basal
circlet is 5 mm. long, the radials each 40 mm. long by 18
mm. wide, and the deltoids 19 mm. long by 11 mm. wide.
In one unfigured syntype 60 mm. long, the stem is
round, approximately 0.5 mm. in diameter, and attached
to three normally disposed basals.
Of importance is the presence of five large U-shaped
oral plates, interradial in position, with a small spiracle
or opening adjacent to the adoral tip of each deltoid
body. These plates apparently closed the oral opening
and fitted tightly against the ambulacral cover plates.
Small openings occur at the adorai ends of the food
grooves, one to each groove at its juncture with adjacent
oral plates, allowing food to pass freely to the mouth.
These openings do not connect with the spiracles internally
but are separated from them by solid stereom
of the oral plates. Thus, food entered in a radial position,
and excreta were emitted in an interradial position.
The small syntype that shows this feature best is 37 mm.
long, with anispiracle 1 mm. wide. A cross-section of this
specimen was etched with acid but it is difficult to see
the exact number of hydrospire folds. Three small indentations
or loops seem to be present on each side of an
ambulacrum. Ambulacra are concave, with 28 side plates
in 10 mm. Radials overlap deltoids.
The type of Pentremites grandis is in a dark-colored
crystalline limestone and is imperfectly preserved. The
calyx is 53 mm. long by 33 mm. wide, ellipsoidal in side
view, with vault 45 mm. long, and preserved part of pelvis
8 mm. long, one side appearing to have a short ambulacrum
(40 mm. long, with radial sinus 13 mm. long).
Each preserved radial is 25 mm. long by 13 mm. wide,
with sinus 20 mm. long by 4 mm. wide. Deltoids are 30
mm. long by 8 mm. wide. Radials overlap deltoids. Each
ambulacrum is concave admedially-abmedially, 45 mm.
long by 7 mm. wide, with approximately 28 side plates
in 10 mm.
The type specimen of the taxon named Pentremites
perelongatus is fragmentary and fractured, occurring in
a dark-colored crystalline limestone. The calyx is 63 mm.
long by 31 mm. wide, broadly ellipsoidal, with vault 40
mm. long and pelvis 23 mm. long. The summit is incompletely
preserved and the calyx plates are thick. Each
radial is 52 mm. long by 12 mm. wide, with sinus 27
mm. long by 5 mm. wide. The deltoids are short, each
14 mm. long by 5 mm. wide, and they appear to overlap
the radials. Each ambulacrum is 40 mm. long by 5
mm. wide, with lancet exposed, and apparently three
slits on each side of an ambulacrum, 27 side plates occurring
in 10 mm. and one pore between pairs of side
plates. Each primary side plate appears to be wedgeshaped,
4 mm. deep, 0.4 mm. wide, and 0.5 mm. long
(abmedially-admedially), with a secondary side plate
normally disposed on the abmedial-adoral corner of each
primary side plate.
Occurrence.—Upper Mississippian, upper part of
Brazer Formation, 6 miles west of Mendon, Utah (PECK'S