ECHINODERMATA - KU ScholarWorks - University of Kansas

84 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS
side of an ambulacrum with short hydrospire canal;
form of calyx widely elliptical. Devonian, New York,
Iowa, Ontario, Michigan.
Remarks.-The genus Nucleocrinus was probably
derived from Elaeacrinus by supression of the superdeltoid
plate internally and reduction in the number of
oral plates to five.
NUCLEOCRINUS ELEGANS Conrad
Plate 29, figures 4-6, 9; text-fig. 168
Nucleocrinus elegans CONRAD, 1842, p. 280, pl. 15, fig. 17.
Description.-Calyx calcitic, subglobular in side view,
rounded pentagonal in top view, 8.5 mm. long by 11 mm.
wide, with concave summit and concave base, and periphery
above mid-height. Stem round, crenellar, 0.75 mm.
in diameter, in basal concavity, with small central round
lumen. Basal circlet pentagonal in basal view, 1.5 mm.
wide, in basal concavity, with three normally arranged
basals. Radials five, short, pentagonal in side view, each
2.5 mm. long by 3.5 mm. wide, mostly on aboral surface,
recurved below in basal concavity, with short, shallow
sinus 1 mn-i, long by 1 mm. wide, and long flaring lips
projected aborally into rounded ridges. Deltoids overlap
radials. The surfaces of the basais and radials are ornamented
by fine growth striae subparallel to plate margins.
Deltoids four, flattened lenticular, each 8 mm. long
by 6 mm. wide, each with a broadly curved V-shaped
radiodeltoid suture at the base, and with two hemielliptical
spiracles at the adorai tip along ambulacral margins.
The ornamentation of the deltoids consists of two parts,
a central triangular portion with apex at adorai end, and
two bordering lenticular portions. The central part has
fine growth ridges parallel to the radiodeltoid suture and
the marginal portions have narrow nodes that are aligned
with the adjacent side plates at a high angle to the
ambulacra. On the anal side three deltoids are visible,
one deltoid being hidden. The visible deltoids are the
two lenticular cryptodeltoids marginal to the ambulacra,
with a central hypodeltoid that is subquadrangular in
shape. The hypodeltoid, on the aboral side of the diamond-shaped
anal opening has growth striae parallel
to the radiodeltoid suture and lateral margins, the central
adorai portion being raised. The lenticular cryptodeltoids
extend from the adorai and lateral sides of the anal opening
to the radiodeltoid suture and have aligned nodes
similar to those of the other four deltoids. The adorai tips
of the cryptodeltoids abut against a large anal oral plate
and each tip has a hemielliptical spiracle along its ambulacral
margin. Thus, ten spiracles in addition to the anal
opening occur around the oral aperture, which is covered
by five large arrow-shaped oral plates, interambulacral
in position. Internally, beneath the anal oral and between
the adorai tips of the cryptodeltoids it is assumed that a
supressed superdeltoid is present. Hydrospire folds presumably
two on each side of an ambulacrum, with a
short hydrospire canal.
Ambulacra five, linear, recurved below, raised above
calyx surface, each 12 mm. long by 1 mm. wide, with
lancet covered by side plates, and 30 side plates in a space
of 10 mm. along an ambulacrum. The side plates consist
of a large raised subquadrangular primary side plate,
with a large triangular secondary side plate on the adoralabmedial
bevelled corner of the primary side plate, and
an inner side plate on the admedial side of each pore,
broadly lenticular in shape. Approximately four main
cover-plate sockets to each side plate occur along the main
food groove, and one pore is present between adjacent
side plates along the radial and deltoid margins.
Occurrence.-Middle Devonian, Hamilton beds, Moscow,
New York.
Type.-Topotype, 19,049, one of two specimens, one
of which is Placoblastus lucina, Gurley collection, Walker
Museum, University of Chicago.
NUCLEOCRINUS MELONIFORMIS (Barris)
Plate 29, figures 1-3, 7-8; plate 30, figures 1-9; plate 32, figure 9;
text-figs. 169-178
Elaeacrinus meloniformis BARRIS, 1883, p. 361; 1885-86, p. 91, pl.
1, fig. 3.
Nucleocrinus meloniformis THOMAS, 1924, p. 428, pl. 36, figs. 10-11.
Description.-Calyx calcitic, 10 mm. long by 7.5 mm.
wide, with periphery above mid-height, vault 10 mm.
long, pelvis 2 mm. long in oblique basal view, with pelvic
FIGURES 168-177. Species of Nucleocrinus CONRAD, Middle Devonian, New York, Ontario.
168. N. elegans CONRAD, Hamilton Group, Moscow, N.Y.
(Univ. Chicago, no. 19,049); part of "B" ambulacrum
showing main, inner, and outer side plates, X45.
169-177. N. meloniformis (BARRIS), Hungry Hollow Formation,
Thedford and Arkona, Ont. (Geol. Survey Canada,
no. 3,662a; Buffalo Soc. Nat. Sci., nos. E148, E15,939,
E21,120); 169, summit and anal areas (no. 3,662a), X15;
170, basal area (no. 3,662a), X15; 171, stem impression
(no. 3,662a), X45; 172, cross section of "E" ambulacrum
(no. E21,120), X15; 173, summit area drawn from polished
section showing hidden superdeltoid (no. E148),
X15; 174, part of weathered "E" ambulacrum, showing
side plates (E15,939), X45; 175, part of "E" ambulacrum,
showing side plates (no. E15,939), X45; 176, anal
area, oral plates lacking (no. E21,120), X15; 177, part of
"B" ambulacrum, showing main, inner, and outer side
plates (no. 3,662a), X75. [Explanation.-An, anal opening;
Bf, brachiolar facet; Bp, brachiolar pit; "C," amb.;
CR, cryptodeltoid; "D," amb.; D, deltoid; HD, hypodeltoid;
ISp, inner side plate; L, lancet; 0, oral plate;
OSp, outer side plate; P, pore; S, spiracle; Sp, main side
plate; Su, superdeltoid; Z, azygous basal.]