268 New Species of Crinoidea from the 



becoming tubuculose, the proboscis proportionally more 

 slender, and the smaller size of the fossil. 



Geological formation and localihj. Burlington lime- 

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

 B. J. Hall of Burlington. 



Actinocrinus limabrachiatus (n. s.). Body turbinate be- 

 low the arms, narrowly truncate at base, somewhat exca- 

 vated for the attachment of the column; arm bases slight- 

 ly projecting; summit unknown. Basal plates short, 

 angularly thickened at the lower margin. First radial 

 plates of medium size, height and width nearly equal. 

 Second radial plates quadrangular, upper and lower mar- 

 gins convex. Third radial plates heptagonal, much larger 

 than the second, wedge-form above, supporting on each 

 side a large, supra-radial, bifurcating plate ; each of these 

 supports on the outer margin a series of brachial plates, 

 and on the inner margin a small supra-radial plate of the 

 second order, each of which gives origin to two arms, mak- 

 ing three arms to each division of the ray, or six to the 

 ray. 



First interradial plate octagonal, supporting two smaller 

 plates in the second range, two in the third, and one in the 

 fourth range. Anal series consisting of about twelve 

 plates: the first hexagonal, smaller than the first radial 

 plates, supporting two in the second range nearly equal 

 in size, one seven sided and the other eight sided ; four 

 smaller plates in the third range ; with the remaining plates 

 irregularly placed above. Surface of plates traversed by 

 a single set of ridges, which passing from plate to plate 

 meet at the centres and form sharp nodes. 



Arms long, slender, simple, composed near their base of 

 a single series of wedge-form plates, and above of a double 

 series of short interlocking plates, each of which has a 

 sharp elevated ridge near and parallel to its upper margin ; 

 the edge of this ridge is directed upwards, and has the ap- 



