BATOCRINID^. 499 



Horizon and Locality. — Keokuk group; Hamilton, Ills., Keokuk, Iowa, 

 and Montgomery Co., Ind. 



Type in the Illinois State collection, Springfield. 



Agaricocrinus crassus WETHEKBy. 

 Plate XXXIX. Figs. Ba, h, and Flate XL. Fig. 4. 



1881. Wetheket; Journ. Ciucin. Soc. Nat. Hist., Vol. IV., p. 178, Plate 5, Figs. 1, la, 6, 

 1885. "W. and Sp. ; EeTision Pateocr., 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 stehiform aspect. Plates massive and a little convex; 

 suture lines moderately distinct. 



Basals covered by the column. Eadials 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 concavitj'. 

 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 loiig, and as a rule hepta- 

 gonal, rarely pentagonal or hexagonal. The number of distichals varies 

 considerabh^ ; 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 is 

 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 



