PALEONTOLOGY OF IOWA. 625 



SURFACE finely granulose or granulose-striate towards the 

 margins of the plates. 



The base is more prominent than the surrounding sub- 

 radial plates ; in which character it differs from C. bulletins, 

 the subradials being less protuberant, and the radials larger 

 and more equal in size. 



This species resembles the C. pentasphericus of TROOST; but the cup is propor- 

 tionally broader and more shallow, the base of the column is smaller, with a penta- 

 petalous perforation, while in TROOST'S specimen the foramen is round. The radial 

 plates of the species under consideration are much wider and proportionally shorter, 

 while the articulating faces are much more extended. 



Cyathocrinus tenncsseea of TROOST also resembles this species; but it is a much 

 smaller form, with smaller and less tumid radial plates. 



Fig. 1 b. Anal side of specimen. Fig. 1 c. Basal view of same. 



Geological formation and locality. In the Keokuk limestone : Warsaw, 

 Illinois 



Cyatliocrinus spurius ( n. s.). 



PLATE XVIII. FIG. 7 & 8. 



Compare Poteriocrinus meekianus, SHUMARD, Geological Report of Missouri, pa. 188, 



pi. A, f. 7 a, b. 



CALYX broad basin-shaped, gibbous, the upper margin ir- 

 regular : base comparatively small. Basal plates elongate, 

 pentagonal. Subradial plates hexagonal, except the one on 

 the anal side, which is heptagonal and very convex. First 

 radial plates wide, the antero-lateral ones longer than the 

 others : second and third radials very short and wide. First 

 anal plate quadrangular, with the lower righthand angle 

 truncated by a small quadrangular plate lying between the 

 two adjacent subradials, the postero-lateral and the anal 

 plate. Arms unknown. Surface granulose. 



This species resembles the preceding in its general form and the thickened charac- 

 ter of the plates; but the subradials are less protuberant, the radial plates are of 

 different proportions, and the articulating faces for the second radials are more 

 oblique to the axis; while the intercalation of a small quadrangular plate on the 

 anal side presents a marked difference in the character of the specimen, and allie a 

 the present species with the Genus POTERIOCRINUS. 



Fig. 7. View of the anal side of specimen. Fig. 8. Basal view of the same. 



IOWA SURVEY.] 79 



