PALAEONTOLOGY OF IOWA. 671 



This species is distinguished by its strong convex or semicylindrical arms and a 

 broader stronger calyx than those previously described. The tentacula have not been 

 observed. 



Fig. 6. The anterior and antero-lateral rays of the column with a part of the adjacent 

 rays. 



FIG. 105. 



D > 



The accom P<W in g diagram illustrates more fully the 

 arrangement of the plates of the base, the subradial and 

 radial plates. 



P 



Geological formation and locality. In the St. Louis limestone : St. Louis, 

 Missouri. 



Forbesiocrinus sliuinardiaiuis ( n. s.). 



PLATE XVII. Fio.l. 



f BODY broadly turbinate with the rays strongly prominent : 

 basal plates forming a narrow rim around the summit of the 

 column ; subradial plates comparatively large, two of them 

 hexagonal and three heptagonal, being truncated at their 

 summit by the interradial plates. Radial plates large, about 

 twice as wide as long, the first ones pentagonal, the second 

 and third hexagonal, and the fourth pentagonal ; secondary 

 plates three between the first and second bifurcation, with 

 the same number between the second and third bifurcation, 

 becoming somewhat abruptly smaller at this point : subdivi- 

 sions of the arms giving ten or twelve to each ray; inter- 

 radial plates twelve or more ; anal plates undetermined ; 

 interaxillary plates four or more. 



COLUMN round, composed of short joints near the summit, 

 gradually becoming larger below. 



This species differs conspicuously from either of the others described, in its broad 

 turbinate form which is abruptly rounded below; the rays are proportionally stron- 

 ger and more abruptly elevated, while the divisions above the first bifurcation are 

 much more abruptly tapering than in any described species. 



