oo ee 
(SU) 
PLATYCRINIDA. 69 
Platycrinus glyptus Hatt. 
Plate LXVIT. Figs. 4, 5. 
1861. Hatz; Descriptions of New Crinoids, p. 16. 
1881. W. and Sp. (var. of P. sewlptus); Revision, Part II., p. 71 (Proceed. Acad. Nat. Sci. Phila., p. 245). 
As large as the preceding species, and resembling it in the form of the 
calyx and style of ornamentation; but the arms more numerous, more deli- 
cate, and comparatively shorter. Dorsal cup goblet-shaped, height and width 
about equal, in very large specimens the height somewhat greater. Surface 
marked by irregular, undulated ridges or rows of obscure nodes, following 
the margins of the plates, and increasing in number in the growing Crinoid ; 
the radials traversed by two diagonal ridges from the facets to the lower 
angles of the plates. Basi-radial and interbasal sutures canaliculate. 
Basal cup comparatively deep, its height equal to one third the height 
of the calyx to the arm bases, the lower end rather abruptly truncated 
and slightly excavated ; interbasal sutures faintly visible. Radials longer 
than wide; the lower faces convex — those meeting the interbasal sutures 
distinctly angular — and slightly beveled along the edges; the sloping upper 
faces forming a rather deep notch, which at the anal side is twice as wide as 
at the other sides, and filled by a-rather large, lozenge-shaped plate. Radial 
facets small, occupying scarcely a third of the width of the plates, and ex- 
tending but little downward. Costals subtrigonal, moderately large. Dis- 
tichals twice as wide as long, and not in contact laterally. The higher orderg 
of brachials to the last axillary slightly constricted in the middle, and gradu- 
ally decreasing in width but retaining the same length, so that the upper 
ones are as long as wide, and even longer in young specimens. Arms rather 
delicate and short for the size of the species; they are very numerous, there 
being from six to seven to each division of the ray, or twelve to fourteen to 
the ray, the bifurcations extending to fully one half the length of the arms, 
and above the palmars given off from the third plate. Structure of ventral 
disk and anus unknown. Column rapidly twisting; the two or three prox- 
imal joints circular, the others elliptic, increasing in length downward; the 
long diameter of the joints fully twice the shorter one. | 
Horizon and Locality.— Upper Burlington limestone; Burlington, Iowa, 
and Henderson Co., Il. 
