PALEONTOLOGY OF IOWA. 579 



porting two smaller hexagonal plates in the second series, and 

 three or four small ones in the third series ; which fill the 

 interbrachial spaces. First anal plate hexagonal, supporting 

 two other heptagonal plates, and above these a small central 

 one, and above this an arch of four small plates ; these sup- 

 port a range of five or six small interbrachial plates. Crown 

 composed of numerous plates of unequal size, all the larger 

 ones prominently tuberculiform. Plates below the arms with 

 obtuse ridges extending to the margins and meeting those 

 from the adjacent plate, converging altogether in a central 

 angular node or transverse ridge. Entire surface granuliferous. 

 Extent of arms and proboscis unknown. 



Fig. 7 a. Anterior side of specimen, Fig. 7 b. Posterior view of the same. 



FIG. 84. 





n 



U(_jr j/ - \( J '- The accompanying diagram illustrates the 



^r- ^^^^ structure of this secies, which corresonds 



structure of this species, which corresponds 

 with the more simple forms of the genus. 



B 



Geological formation and locality. In the Burlington limestone : Bur- 

 lington, Iowa. 



Actinocriims multiradiatus. 



PLATE X. FIG. 9. 

 Actinocrinus multiradiatus : SHXTMAKD, Trans. Acad. Scien. St.Louis, 1857, p. 7. 



BODY urnshaped : base truncate ; summit convex, with a 

 subcentral proboscis. Basal plates large ; the margins ex- 

 tended in a thickened expanded rim, which is deeply notched 

 at the line of division between the plates; a groove con- 

 tinuing along the suture, and extended to the centre of the 

 next succeeding plate, margined by sharp angular ridges. 



