224 THE CEINOIDEA CAMEEATA OF NOETH AMEEICA. 



als large, lying almost horizontally, except their proximal ends, which bend 

 abruptly inward and take part in the concavity ; the upper faces broadly 

 truncated. 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. Nothino- 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 outline, 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 hmestone, 

 Burlington, Iowa. 



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. hiirUngtonensis is a very large example of 

 R. WMtei. That it has one or two additional interbrachials, that the 

 calyx 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 Benedict! S. A. Miller. 



1893. Advance Sheets Eighteenth 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 



