556 GEOLOGICAL SURVEY OF IOWA. 



length of the plate, and bordered by an elevated rim. The 

 single anal plate remaining is heptagonal. 



SURFACE marked by minute pustulose granulations. Column 

 small. 



Fig. 7 a. Anal side of specimen (on some of the plates imperfectly represented). 



Fig. 7 b. Base of the same (the lines of division between the basal plates are not clearly 

 shown in some of the impressions) . 



Geological formation and locality. In the Burlington limestone : Quincy, 

 Illinois. 



GENUS llHODOCRINUS (MILLER). 



FIG. 73. 

 a GENERIC FORMULA. 



Basal plates 5, united in a regular pentagon. 



%O"^ fj r=7 * Subradials 5, hexagonal. 



O Vuir\aOa Radial plates, 3X5. 



iL xM%^ J( , Brachials one or two, united to the calyx. 



Interradial plates, 6 to 8 X 4. 

 Anals, 10 to 12. 



Q w c# Interaxillarics, 1X5. 



1 y Arms 10 to 20, which are bifurcated two or three times 



in the course of their length. 



THESE characteristics, together with the description of the 

 following species, will serve to distinguish this generic form 

 among all the other carboniferous crinoids. 



The basal plates are often small,. and may be overlooked. 

 The interradial, anal and interaxillary plates are subject to 

 variation in number. 



Rhodocrinus woitheni ( n. s.). 



PLATE IX. FIG. 8 a, b, c. 



BODY subglobose, very gibbous or ventricose below and 

 somewhat contracted above ; base a little flattened. Basal 

 plates small, regularly pentagonal. Subradial plates hexago- 

 nal, about as long as wide, abruptly curving upwards in the 

 middle. First radials heptagonal, a little longer than wide. 

 Second and third radials much smaller. First interradials 



