ECHINODERMATA - KU ScholarWorks - University of Kansas

42 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS
limbs aborally. There are seven or eight hydrospire slits
in the sides of each cryptodeltoid, extending to the adjacent
radial limbs. The low superdeltoid, with spiracular
slits on each side, is bluntly arrow-shaped, and together
with the other four deltoid lips and five lancet stipes, helps
border the oral opening.
Ambulacra five, linear, projecting down the sides of
the calyx, each 4 mm. long by 0.75 mm. wide, with lancet
completely covered by side plates, and 35 side plates in
10 mm. The side plates appear to be normally disposed,
with the broadly triangular secondary side plate resting
upon the abmedial-aboral bevelled corner of the primary
side plate. The plates are worn so that details are obscure.
The surfaces of the calyx plates are ornamented with fine
growth lines parallel to plate margins.
Occurrence.—Middle Devonian, coral zone of Widder
beds, Hungry Hollow Formation, Ausable River valley,
2.5 miles northeast of Arkona, Ontario, Canada.
FIGURES 46-50. Species of Phaenoblastus FAY, n.gen., and Pleuroschisma REIMANN.
46-48. Phaenoblastus caryophyllatus (DEKONINCK & LE-
"lox), Lower Carboniferous, Tournaisian, Tournai, Belgium
(Univ. Chicago, no. 19,082; U.S. Natl. Mus., no.
S3,268); 46, morphological features of anal area and part
of "DE" interambulacrum (no. 19,082), X15; 47, part
of "C" ambulacrum, showing main and outer side plates
(no. 19,082), X45; 48, oblique view of part of ambulacrum,
showing surface and cross section (no. S3,268),
X37.5. 49, 50. Pleuroschisma ontario REIMANN,
Middle Devonian, near Arkona, Ont. (Univ. Michigan,
no. 35,033); 49, morphological features of anal area and
part of "DE" interambulacrum (no. 35,033), X15; 50,
part of "A" ambulacrum showing main and outer side
plates (no. 35,033), X90. [Explanation.—An, anal opening;
Bf, brachiolar facet; Bp, brachiolar pit; "C," amb.;
C, canal; CR, cryptodeltoid; "D," amb.; Db, deltoid
body; Dc, deltoid crest; DI, deltoid lip; ED, epideltoid;
HD, hypodeltoid; Hs, hydrospire slit; L, lancet; 0, oral
opening; OSp, outer side plate; R, radial; RI, radial limb;
Sp, main side plate; Ss, spiracular slit; Su, superdeltoid.1