228 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
are dark, and Megistocrinus and Latocrinus rather intermediate ; but while 
Rhodocrinus Kirbyi is very dark, R. nanus is light colored, and R. water- 
sianus intermediate between them. 
Rhodocrinus nanus M. and W. 
Plate XI, Figs. 7a, b; and Plate XII., Figs. 2a, b. 
1866. Merk and Wortuen; Proceed. Acad. Nat. Sci. Phila., p. 254. 
1868. Merex and Wortuen; Geol. Surv. Illinois, Vol. III., p. 476, Plate 18, Figs. 2a, d. 
1885. W.and Sp.; Revision Paleocr., Part II., p. 212. 
1889. W. and Sp.; Geol. Surv. Illinois, Vol. VIIL., p. 182, Plate 16, Fig. 4; and Plate 17, Fig. 15. 
Syn. Rhodocrinus sculptus S. A. Mituer; 1890, Deser. New Genera and Species of Echin., p. 42, 
Plate 7, Fig. 11. 
Syn. Rhodocrinus cevlatus 8. A. Miter; 1890, ibid., p. 43, Plate 7, Fig. 10. 
Calyx subglobose, the sides regularly convex, except in specimens with 
very protuberant basals, in which they appear to be nearly straight; the 
base truncate and slightly impressed. The plates along the rays marked by 
rounded ridges, which vary somewhat in prominence. These ridges in some 
specimens are confined almost entirely to the radial series, giving to the 
calyx a pentagonal outline, but in others they run to the basals, interradials 
and anal plates, traversing the sutures, and passing from plate to plate. The 
plates are more or less convex, and their outlines well defined. 
Infrabasals small, impressed, slightly projecting beyond the column. 
Basals large, a little protuberant, the calyx resting on their lower margins, 
which are rounded and form a low rim around the concavity. Radials nearly 
as large as the basals; the costals about of equal size, but one third smaller 
than the radials. Distichals generally five, of which only the first and 
larger one takes part in the calyx; the others which are of nearly uniform 
size and quadrangular, except the upper which is axillary, are free arm 
plates. The inner branches of the arms divide again on the third joint, and 
there is also occasionally a bifurcation from the outer branch in a posterior 
ray. The arms taper but little, are long, and biserial after the last bifur- 
cation. The arm joints are narrower than in &. Kirbyi, and their backs more 
rounded ; the pinnules stronger and less closely packed than in that species. 
First interradials half the size of the radials; followed by two interbrachials 
nearly as large; the succeeding plates considerably smaller, and their ar- 
rangement somewhat irregular. Anal interradius wider than the others, and 
enclosing a continuous row of anal plates, which rest upon the truncated 
upper face of the interradial. The first anal plate is as large as the radials, 
but the interbrachials at both sides of it are smaller than the corresponding 
