224 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
als large, lying almost horizontally, except their proximal ends, which bend 
abruptly inward and take part in the concavity; the upper faces broadly 
truneated. Radials hexagonal, about as wide as long. Costals as long as the 
radials, but generally a little narrower. Distichals generally represented by 
only one row of plates in the calyx, which are excavated at the upper faces 
to form the arm openings, of which there are two to the ray. Nothing is 
known of the arm structure. The interradial spaces are occupied by 1, 2, 
3, and two large plates, followed by two or three smaller ones. The 
anal interradius has a few more plates in the upper rows. Ventral disk 
small, slightly convex, pentangular in outlme, and composed throughout of 
small, irregular, slightly convex pieces, which increase in size as they ap- 
proach the arm regions. Anus subcentral, at the end of a short tube or 
elongate protuberance, which gives to the disk an irregularly conical form. 
Column small, not filling the basal concavity; it is round, and there is an 
alternation of larger and smaller plates. Axial canal of medium size and 
stelliform. 
Horizon and Locality. — Lower part of the Lower Burlington limestone, 
Burlington, Towa. 
Types in the University Museum at Ann Arbor. 
Remarks.— We have examined a number of specimens of this rare 
species, including the types, and are of the opinion that the specimen 
which Hall described as var. burlingtonensis is a very large example of 
R. Whitei. That it has one or two additional interbrachials, that the 
xalyx is proportionally a little shorter and the basal concavity deeper, is 
readily explained by extravagant growth. The species occurs in the low- 
est layers of the Lower Burlington limestone, and the calyx sometimes 
attains a size of two inches in diameter. 
Rhodocrinus Benedicti 8. A. Mitrrr. 
1892. Advance Sheets Highteenth Rep. Geol. Survey Indiana by Gorby, p. 15. 
Calyx small and globular, except the tegmen, which is slightly conical. 
Dorsal cup nearly as high as wide, widest at the middle; the sides evenly 
rounded to the arm bases; the base concave. Plates convex, some of them 
angular, and the principal ones covered with radiating ridges. Suture lines 
distinct. 
Infrabasals small, forming a flat pentagonal disk. Basals the largest 
plates of the calyx, highly convex in the central part, with ridges extending 
