ECHINODERMATA - KU ScholarWorks - University of Kansas

BLASTOID STUDIES 91
189 191 192
FIGURES 188-192. Species of Pentremites SAY and Petaloblastus FAY, n. gen.
188. Pentremites godoni (DEFRANcE), Upper Mississippian,
Gasper Formation, Bowling Green, Ky. (U.S. Natl.
Mus., no. 139,104); partial cross section of "A" ambulacrum,
oral view, X17.5. 189-192. Petaloblastus ovalis
(GoLD Fuss), Lower Carboniferous, Etroeungtian, Cromford
bei Ratingen, Germany (Harvard Mus. Comp.
Zoology, no. 316); 189, summit and anal areas, drawn
from polished section, X15; 190, partial cross section of
"?C" ambulacrum, oral view, X45; 191, part of ambulacrum,
showing lancet and side plates, X45; 192, part of
ambulacrum, X30. [Explanation.—An, anal opening;
Bf, brachiolar facet; Bp, brachiolar pit; "C," amb.; C,
canal (radial); D, deltoid; ED, epideltoid; H, hydrospire;
HD, hypodeltoid; L lancet; OSp, outer side plate; P,
pore; R, radial; RI, radial limb; Sp, main side plate.]
panded supplementary basais immediately above the stem
and overlapping the basals. Radials five, each elongate
hexagonal in side view, 4.5 mm. long by 2.5 mm. wide,
with long wide, shallow sinus 2.5 mm. long by 3.75 mm.
wide, and prominent bluntly pointed radial lip. The
radials overlap deltoids so that the V-shaped radiodeltoid
suture has its apex pointed adorally, which is opposite that
of most blastoids. This opposite relationship is due to the
fact that the radial limbs meet at a point along the midline
of each adjacent deltoid and the suture is seen along
the wide sloping sinus.
Deltoids four, visible in side view, each 1.5 mm. long
by 0.75 mm. wide, V-shaped with apex directed adorally,
each notched adorally by a large oval spiracle that separates
the deltoid lip from the deltoid body externally.
Internally these two parts are connected by a deltoid septum.
On the anal side there appear to be two anal deltoids,
an epideltoid adjacent to the oral opening, and a
V-shaped hypodeltoid on the aboral side of the anispiracle.
The superdeltoid has two thick deltoid septa on its aboral
face that separate the anal opening from the adjacent
hydrospire canals internally. The hypodeltoid overlaps
these septa, thus covering the adoral part of the anal
opening. Therefore, five openings surround the oral
aperture, consisting of four spiracles in addition to the
anispiracle. There are four hydrospire folds on each side
of an ambulacrum.
Ambulacra five, broad, petaloid, with lancet exposed
its full width along each ambulacrum, and 40 side plates
in a space of 10 mm. along an ambulacrum. The exposed
lancet is approximately 1 mm. wide, the side plates 0.5
mm. wide on the sides, and the ambulacra are each 4.5
mm. long by 2 mm. wide. The side plates are normally
disposed, with a subtriangular outer side plate resting on
the bevelled abmedial-adoral corner of each primary side
plate, one pore between adjacent side plates along the
deltoid and radial margins, and approximately four coverplate
lobes to each side plate along the main food groove