030 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
| 
| 
(?) Periechocrinus Whitei (H11). | 
Plate XLVI. Figs. 1, 2, 3, and Plate LI. Figs. 9, 10. | 
| 1861. Actinocrinus (Megistocrinus) Whitei —Hati; Prelim. Descr. New Crin., p. 2, and Bost. Journ. Nat. 
We) Hist., p. 271. . 
| 1873. Megistocrinus (Saccocrinus) Whitei —Mnzx and WortuEen; Geol. Rep. Iinois, Vol. V., p. 397, 
Plate 6, Figs. la, 0, e. 
1877. Meyistocrinus Whitei —S. A. Mirumr; Amer. Paleoz. Foss., p. 83. 
aa 1881. Periechocrinus Whitei—W. and Sr.; Revision Paleocr., Part II., p. 188; and Whitfield; Amer. | 
Beh | Mus. Nat. Hist., 1893, Vol. L., p. 27, Plate 2, Fig. 29. 
| Syn. Actinocrinus (Pradocrinus) amplus —Mxnx and Wortuen; 1861, Proc. Acad. Nat. Sci. Phila., 
p. 188, also 1868, Geol. Rep. Illinois, Vol. IIT., p. 470, Plate 16, Fig. 2. 
Syn. Actinocrinus amplus — 8. A. Mitter; Amer. Paleoz. Foss., p. 66. | | 
Syn. Periechocrinus amplus—W. and Sr.; Revision Paleocr., Part II., p. 131. 
rt, Calyx depressed bell-shaped, height and greatest width nearly equal; 
} 1 | | tegmen flattened or depressed convex; plates thin, and without ornamenta- 
tion; radial ridge but faintly indicated. 
Basals forming a shallow basin, abruptly truncated at the bottom for the 
reception of the column; the latter occupying two thirds the diameter of the 
base. Radials large, length and width subequal, their upper lateral faces 
shorter than the corresponding lower ones. First costals scarcely more 
than half the size of the radials, proportionally a little longer, and hexan- 
gular; second costals much smaller than. the first, and pentangular. The 
Jatter support four distichals, which according to the age of the specimen are 
either all fixed or in part free. The distichals short, even the first which is 
twice as long as the succeeding ones. Arm facets projecting, arranged in 
pairs, the spaces between the rays twice as wide as those between their main 
| divisions. Arms long, gradually decreasing in size upwards, very delicate at 
| the top, biserial above the first to the third distichal. Pinnules long, closely 
| packed and rather stout; their joints twice as long as wide. First inter- 
brachial as large as the first costals or larger; supporting two smaller plates 
| | in the second range, three in the third, and a number of irregular pieces 
| above. Anal interradius very wide; each one of the three plates resting upon 
the first anal almost as large as the one plate of the regular sides. They are 
followed by three smaller pieces, and these in large specimens by as much as 
twenty or more plates, of which the upper row connects with the plates of 
the tegmen. The disk plates are small throughout, and closely resemble the 
interambulacral plates of some Pentacrinide. Anus excentric, rising but 
little above the general surface of the tegmen. Column stout, the joints 
