Carboniferous Rocks of the Mississippi Valley. 319 



towards the base. The supra-radial plates are likewise 

 angular, as well as the arm plates, which are somewhat 

 nodose. The patelloid plates are distinct in the lower part 

 of the body, and show as simple undulations in the arms; 

 entire surface granulose. Column large at the summit, 

 composed of thin, alternating larger and smaller plates. 



This species ditfers from the F. Thiemei in having the 

 radial plates less distinctly angulated on the back, and 

 narrower in proportion to the height, and in the long 

 spines upon the third radial plates, and in possessing inter- 

 radial plates. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collection of C. A. White. 



Forbesiocrinus jnvenis (n. s,). Body small, sub-globose, 

 truncated at base rather largely. Basal plates short, show- 

 ing only as a thin edge of a disc outside of the column. 

 Sub-radials of medium size, pentagonal and hexagonal, 

 wider than high, obtusely pointed above. Radial plates 

 four in each series : the first largest, sub-heptagonal, once 

 and a half wider than high ; second and third radials short 

 and broad ; fourth radial very broad in proportion to 

 its height, obtusely pointed above, and supporting an 

 arm on each side. Arms dividing on the fourth plate 

 above, and again dividing once more at least ; strong and 

 rounded on the back, composed of a single series of short, 

 strong plates, rapidly diminishing in size at each bifurca- 

 tion. Interradial and anal series consisting of one plate 

 each, resting upon the edges of the first radials and be- 

 tween the second radials of the adjacent rays, the rays 

 becoming free above the second radial plate. The small 

 patelloid plates are indicated by the strong curvature of 

 the suture lines of the radial plates, becoming more dis- 

 tinct in the arm plates. Surface apparently smooth. 

 Column proportionally large, rapidly tapering below, com- 

 posed of thin, equal plates, with a large central perfora- 

 tion. 



