BATOCRINID&. 499 
Horizon and Locality. — Keokuk group; Hamilton, Ils., Keokuk, Iowa, 
and Montgomery Co., Ind. 
Type in the Illinois State collection, Springfield. 
Agaricocrinus crassus WETHERBY. 
Plate XX XIX, Figs. 2a, b, and Plate XL. Fig. 4. 
1881. WestuErsy; Journ. Cincin. Soc. Nat. Hist., Vol. IV., p. 178, Plate 5, igs. 1, la, 6. 
1885. W. and Se.; Revision Paleocr., Part III., p. 105. 
A large and robust form; calyx more distinctly lobate than in any other 
species of this genus. Dorsal cup almost twice as wide as high, its base but 
very little concave, the second row of interbrachials abruptly bent upward, 
and the brachials above the first costals inflected, which combined gives to 
the calyx a decidedly stelliform aspect. Plates massive and a httle convex ; 
suture lines moderately distinct. 
Basals covered by the column. Radials quite irregular, the two posterior 
ones fully one half longer than the others, all hexagonal in outline, their 
extreme lower ends bending inward to form the sides of the basal concavity. 
First costals as large as the radials, generally quadrangular, the lower face 
narrower than the upper, and about equal to the length. Second costals the 
largest plates of the dorsal cup, twice as wide as long, and as a rule hepta- 
gonal, rarely pentagonal or hexagonal. The number of distichals varies 
considerably ; all ray divisions with palmars have but one distichal, which, 
being axillary, is followed by 2 X 2 palmars; those without palmars have 
two successive distichals, which are from three to four times as long as the 
lower arm plates. Arm facets of the same ray contiguous to the third arm 
plate, and directed horizontally. Arms three to four in the two posterior 
rays, in the other rays their number is limited to two. Interradial spaces 
comparatively wide, especially at the anal side; the first interbrachial gen- 
erally rises to the middle of the second costals, and is elongate, bending 
slightly upward. Of the second range of interbrachials only the lower end 1s 
visible in a dorsal aspect; they are rather broad, extend to a level with the 
arm openings, and are followed by a number of from eight to ten interambu- 
lacral pieces, one or two of them covering over the ambulacra. First anal 
plate longer than the posterior radials; the three plates above almost as 
wide as the corresponding single piece of the other sides; the next row 
consists of four or five smaller plates, and these are followed by numerous 
irregular pieces forming a slightly elevated area, which at midway between 
