626 GEOLOGICAL SURVEY OF IOWA. 



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

 Illinois. 



Cyathocrinus protuberans (n.s.). 



PLATE XVIII. Fio. 9. 



CALYX depressed subturbinate, and somewhat obtusely 

 pentagonal. Basal plates extending beyond the circumference 

 of the column about half its diameter : centre perforated by 

 a moderately large pentapetalous foramen. Subradial plates 

 longer than wide, subangularly tuberculiferous in the centre, 

 and distinctly impressed in the spaces between. Radial plates 

 broad, thick, and tumid in the middle ; the anterior and 

 antero-lateral ones being larger than the others. Second 

 radials short and wide. Third radials twice as long as the 

 second : the arm-plates diverging from the upper sloping 

 sides ; the divisions sending off branches on each side al- 

 ternately from the thickened margins of every fourth plate, 

 beginning at the seventh or eighth plate from the base. Anal 

 plate small, quadrangular. Column round, composed of al- 

 ternating longer and shorter joints. Surface granulose or 

 granulose-striate . 



(In some of the impressions, the subradial plates are not 

 represented as sufficiently prominent.) 



In one of the arms, which is partially preserved, the 

 branches on one side are seen ; and on the opposite side of 

 the same arm, the branches originate from the second plate 

 above. 



This species resembles the two preceding, C. tumidus and C. spurius ; but the 

 obtusely angular character of the nodes or tubercles on the subradial plates allies it 

 also with C. stellatus, where these nodes are spiniform. The space between the nodes > 

 including the margins of the adjacent subradial plates, the base of the radials, and 

 the apex of the basal plates, is distinctly concave and impressed. In these respects, 

 and in the character of the upper radial plates, this species is very distinct. 



Fig. 9. View of the left antero-lateral side of specimen, 



