770 



THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Dichocrinus COnuS Meek and WORTHEN. 

 Plate LXXV. Fig. 6. 



I860. Meek and Worthen; Proceed. Acad. Nat. Sci. Phila., p. 381; and Geol, Rep. Illinois, Vol. II., 



p. 169, Plate 16, Pigs. 5a, b. 

 1881. W. and Sp. ; Revision Pal^ocr., Part II., p. 83. 



Large for this genus. Calyx obconical ; width and length as four to 

 five ; constricted at the upper end ; distinctly hexagonal in outline, a keel- 

 like angularity proceeding from the radial facet all the way to the lower 

 end of the basals. Plates thin, without ornamentation, and united by closely 

 fitting linear sutures. 



Basal cup obconical, nearly as high as the radials, the sides perfectly 

 straight ; the basal concavity unusually small, being not larger than the 

 width of the column; the re-entering angles at the upper face deep. Radials 

 varying in size, their length from once and a half to twice their width, 

 the antero-latei-al ones wider than the others, but all increasing in width 

 upwards; facets surrounded by a thickened angular rim, occupying nearly 

 one third the width of the plates, and extending down to about one fifth 

 their length, forming large limbs at the sides, which bend decidedly in- 

 ward. Anal plate narrower than the radials, hexangular, fully twice as 

 long as wide; the sides nearly parallel. All other parts of the species 

 unknown. 



Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 



Type in the Illinois State collection, Springfield. 



Remarls. — Differing from all other species in the larger size, the angu- 

 larities which extend to the whole length of the cup, the constriction of the 

 cup at the upper end, and the great depth of the radial facets, with well 

 defined limbs at the sides. 



Dichocrinus inornatus W. and Sp. 

 Plate LXXVII. Figs. 12a, h. 



1890. W. and Sp. ; Geol. Rep. Illinois, Vol. VIII., p. 190, Plate 16, Figs. 1 and 2. 



Not above medium size. Calyx subovoid; the sides uniformly curving 

 from the column to the arm bases ; the ventral disk almost flat. Surface of 

 plates devoid of ornamentation or other markings, except a faint longitu- 

 dinal angularity along the middle of the radials. 



