266 New Species of Crinoidea from the 



culose, while the intermediate ones are small and de- 

 pressed. 



This species resembles the A. clavig-erus, (Supp. Iowa 

 Rep. page 44,) but difl'ers in its larger and more protruding 

 base, and in the depression of the interradial plates, caus- 

 ing the radial series to stand out in the form of ridges, 

 while the A. clavig-erus is symmetrically smooth below the 

 arms. 



Geological formation and localihj. Burlington lime- 

 stone, Bnrlington, Iowa. Collections of C. A. White and 

 B. J. Hall of Burlington. 



Actinocrinus cla'lia (n. s.). Body broadly caliculate ; 

 dome highly convex, surmounted by a sub-central probos- 

 cis. Basal plates short, somewhat projecting laterally, 

 salient at the outer margins, and deeply indented at the 

 suture lines. First radial plates of medium size, little 

 wider than long. Second radials small, quadrangular. 

 Third radials small, pentagonal or heptagonal, obtusely 

 wedge-form above, supporting on each side, in the ante- 

 rior ray, a series of three brachial plates, giving origin to 

 two arms. In the other rays they support on each side a 

 series of two supra-radial plates, the upper one of which 

 is wedge-form above, and supports on each sloping side a 

 series of two brachial plates, giving origin to four arms 

 from each, making the brachial formula A = 18. 



Interradial series consisting of three to four j)lates 

 each ; the first eight-sided, about two thirds as large as 

 the first radial plates, supporting two smaller, somewhat 

 elongate plates in the second range, with sometimes an 

 intercalated plate above. First anal plate heptagonal, a 

 litth' smaller than the first radial plates, supporting three 

 in the second range and two in the third. Surface of the 

 body plates sub-spinous or strongly tuberculose ; those of 

 the radial series are elevated in the centre, giving the ap- 

 pearance of a ridge j)assing along the ray. Dome com- 



