680 GEOLOGICAL SURVEY OP IOWA. 



wider than long, and slightly spreading above. Second radials 

 twice as long as wide, thickened, rounded exteriorly and 

 concave at the sides, the margins spreading to the sutures. 

 Arms composed of elongated joints, which, near the base, 

 are more than twice as long as wide, rounded externally, and 

 concave at the sides. 



COLUMN round or obtusely pentagonal, composed near the 

 body of thickened equal joints. 



This species differs from any other of the genus, in the elongate second radials and 

 the long arm-joints, which are simple, as far as observed. 



Fig. 2. The anterior side of a specimen preserving the lower joints of the arms. 

 FIG. 107. 



The accompanying diagram illustrates the form and 

 proportions of the plates of the body and the elongate 

 lower plates of the arms and tentacula, which are distin- 

 guishing features of this species. The lateral extensions of 

 *^ e secon< ^ radial plates, beyond the curved line, represent 

 the thin articulating margins, which are usually not visible 

 9J in the specimens examined. 

 Geological position and locality. In the Kaskaskia limestone : Chester, 

 Illinois. 



Scaphiocrinus scoparius ( n. s.). 



PLATE XXV. Fia.3 a, b. 



BODY small, regularly turbinate below, and cylindrical 

 above to the first bifurcation of the arms. Basal plates minute, 

 forming a small pentangular disc above the column : sub- 

 radial plates very small, regularly hexagonal. First radials 

 pentagonal, wider than long, straight above. Second radials 

 pentagonal, wedgeform above, a little longer than wide, sides 

 parallel, and slightly converging above ; each second radial 

 giving origin to a pair of arms, the lower joints of which are 

 twice or thrice as long as the succeeding ones. Arms bifur- 

 cating on the sixth or seventh plate from the base, composed 

 of plates which are alternately thicker and thinner on their 

 opposite sides ; those above the bifurcation minute, qua- 

 drangular. 



