PALEONTOLOGY OF IOWA. 555 



ing plates. Subradial plates hexagonal (except the one on the 

 anal side), wider than long, prominent in the middle. Radial 

 plates subheptagonal, wider than high : articulating scar 

 deeply impressed, and margined by an elevated ridge. Arms 

 composed of a single series of joints which are sometimes 

 of unequal length, bifurcating on the second joint from the 

 base, and again upon the second joint above the first bifur- 

 furcation ; branches divaricating, their number unknown. 



SURFACE finely granulose. Column composed of alternating 

 longer and shorter joints of unequal size near the body, be- 

 coming much longer and of nearly equal length below : 

 articulating surfaces coarsely and deeply striated. 



This species differs from C. malvaceus in the larger basal plates and less gibbous 

 subradials, which are obtusely angular in the middle, rather than broadly rotund : 

 the articulating scar on the radial plates is proportionally deeper, and the surface 

 markings are quite distinct. 



Fig. 5. An individual preserving a portion of the column and several of the arms to the 

 second bifurcation. The upper angles of the basal plates should be shown in 

 the figure. 



Geological formation and locality. In Burlington limestone : Burlington, 

 Iowa. 



Cyathocriims rotundatus ( n. s.). 



PLATE IX. FIG. 7 a, b. 



BODY subglobose, somewhat inequilateral, being longer on 

 the anal side. Basal plates moderately large, the lateral and 

 superior sides equal. Subradial plates hexagonal ; length and 

 breadth equal, except that on the anal side, which is hepta- 

 gonal and longer than the others : the lateral and superior 

 sides equal in all. Radial plates pentagonal ; the lateral and 

 basal sides equal, and each equal in length to the upper 

 side : width across the middle a little greater than the 

 length, gradually narrowing from the lower lateral angles, 

 indented upon the upper margin and marked with a small 

 articulating scar, which occupies about half the width of the 

 upper margin and extends downward about one-third the 



