RHODOCRINID&. y 
NS 
23 
forming a circular pit, which is but partly filled by the upper joint of the 
column. Plates without ornamentation, a little convex, the suture lines 
slightly grooved. 
Infrabasals small, concealed by the column. Basals as large, or even 
larger than the radials, their lower ends bending abruptly inward to take 
part in the pit, the upper portions curving gently outward and upward. 
Radials heptagonal, a little wider than long, and twice as large as the 
costals, which are quite narrow. Distichals free from the first up; the 
upper faces of the latter slightly excavated to form the ambulacral opening. 
The free distichals consist of about eight plates, which are very short; the 
upper one axillary, supporting two arms, of which one branches again on 
the eighth joint, while the other remains simple. Arms cylindrical, of nearly 
uniform size, biserial above the last bifurcation; the plates very short and 
transversely arranged. Pinnules rather stout and in contact; the joints 
twice as long as wide, with deep ambulacral grooves. Interradial areas not 
depressed ; arranged: 1, 2, 3, 2, succeeded by three or four more pieces. 
The anal side has three plates in the second row. Ventral disk composed of 
but few plates; it is somewhat elevated at the margin, almost flat in the 
middle. Orals well defined ; surrounded by two rows of rather large inter- 
ambulacral pieces, which meet with the interbrachials. Anus subcentral, 
opening through the disk. Column round ; axial canal small and stellate. 
Horizon and Locality. — Lower Burlington limestone, Burlington, Iowa. 
Type in the Museum of Comparative Zoblogy, Cambridge. 
Rhodocrinus Whitei Hatt. 
Plate XIII. Figs. 1a, b,c, and Plate XV. Figs. Ga, b. 
1861. Hat; Description of New Spec. Crinoids, p. 9. 
1861. Hari; Bost. Journ. Nat. Hist., Vol. VIT., p. 324. 
1872. Harr; N. Y. State Mus. Nat. Hist., Bull. L., Plate 6, Figs. 19, 20, 21. 
1881. W. and Se.; Revision Paleocr., Part IT., p. 213. 
Syn. Rhodocrinus Whitei, var. burlingtonensis Haut; 1861, Bost. Journ. Nat. Hist., Vol. VIL., p. 325. 
The largest known American species. Calyx depressed sub-globose, a 
little wider than high ; the lower portion flattened and formed into a deep 
concavity ; the sides decidedly bulging to the first costals, then contracting 
to near the arm bases. All plates of the dorsal cup to the top of the cos- 
tals of nearly the same size, all strongly convex, and without ornamentation. 
Infrabasals of medium size, slightly projecting beyond the column. Bas- 
