" _ . a . or 
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SS a eee 
— 
712 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Platycrinus eminulus HaAtr. — 
Plate LX VILLI. Figs. 13a, 6, ¢. 
1861. Hatt; Descr. New Spec. of Crinoids, p. 17. 
A smaller species than P. regahs ; the dorsal cup more spreading, and 
more distinctly pentangular ; the base proportionally smaller and flatter, 
either smooth or marked by obscure concentric bands parallel to the mar- 
gins of the plates, sometimes separating into distinct lachrymose nodes. 
Basi-radial and interradial sutures deeply grooved, and the margins of ad- 
jacent plates thickened and highly beveled. 
Basals forming a shallow basin, of which the median portions are rather 
deeply depressed, and only the beveled outer margin is visible from a side 
view ; interbasal sutures rather distinct. Radials forming an angle of about 
45° with the bottom of the cup; once and a half—or less—as wide as 
long, and not quite one half wider at the top than at the bottom: The 
notches toward the regular interradial spaces shallow, that at the anal side 
considerably deeper; the median portions strongly thickened to form the 
facet, which occupies about one third the width of the upper face. The 
facet is semi-ovate, deeply notched at the upper end, the surface perfectly 
flat and directed horizontally. Costals almost as long as wide, wider at the 
top than at the bottom, the upper angle obtuse. Distichals, palmars, and 
post-palmars, two to each order; the plates wider than long, gradually 
decreasing in size; but the upper one of each order larger than the lower, 
wider and also higher. Arms eight to the ray, given off as in the preced- 
ing species; quite heavy, very little tapering, and curving outward. Ventral 
disk of about the same height as the dorsal cup; composed of a few large 
plates. ‘The orals sharply tumid; the posterior one resting between the 
other four, somewhat larger, and provided with a stronger node. The 
ambulacral plates large, but smaller than the orals, arranged quite regularly 
in two rows. The interambulacral spaces depressed, formed of three trans- 
versely arranged pieces, of which the middle one is as large as the orals, but 
pertectly flat; that on the anal side larger and curving longitudinally; the 
opening located in the middle of a small, rounded protuberance, composed 
of small pieces. 
Horizon and Locality. — Lower Burlington limestone, Burlington, Iowa. 
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