488 THE CMNOIDEA CAiXERATA OF KORTH AMERICA. 



Agaricocrinus Americanus (Roemek). 

 Plate XLII. Figs. 1, 2a, h. 



1855. Amphoracrinus americanus — Roemek; Letliaea Geogn. (Ausg. 3), p. 250, Plate IT., Figs, loa, b. 

 1365. Agaricocrinus americanus — Shtjmahd; Trans. Acad. Sci., St. Louis, Vol. II., p. 351. 

 1881. Agaricocrinus americanus — W. and Sp. ; Revision PalEeoor., Part II., p. 111. 



(Not Imphoracrinus americanus Q,VEiisTE-DT, Handb. der Petrefactenkunde [Aufl. 3], p. 957, Plate 77, 



Pig. T^^ Agaricocrinus Wort/teni HaW.} 

 Syn. Agaricocrinus dissiniilis S. A. MiLLUli; Ady. Sheets 17th Rep. (Jeol. Survey Indiana, p. 55, 

 Plate 8, Pig. 11. 



Calyx hemispherical, more or less deeply excavated at the bottom. The 

 upper half of the interbrachials and the arm facets are the only parts of the 

 dorsal cup visible from a side view ; the basals, radials, and costals occupy 

 the basal concavity, and the distichals and palmars stand more or less at 

 right angles to the vertical axis of the calyx. All plates of the dorsal cup 

 show a slight tendency to become convex, and the suture lines are moder- 

 ately distinct. 



Basals very small, and covered completely by the upper stem joint. 

 Radials small, very little larger than the first costals ; their extreme lower 

 edges bending abruptly inward to form the concave base. First costals 

 quadrangular with convex sides. Second costals and first distichals larger 

 than the radials, and their surface generally somewhat more convex than 

 that of the plates below. The first distichal of the three anterior rays, in 

 which tJiere are two arms, is followed by a cuneate second, which interlocks 

 with the first, and with the three lower arm plates of the inner rows. In 

 the two posterior rays, which have three arms — exceptionally four — the 

 divisions next to the anal side have but one distichal and two palmars. 

 Arms heavy at the base, but tapering all the way up to the tips, where they 

 end in a sharp point. They are composed of two rows of short joints, with 

 slightly convex outer faces, which give off rather stout and long pinnules. 

 Interradial spaces somewhat depressed at the arm bases ; the anal side very 

 much the widest. First anal plate longer than the radials, and longer than 

 wide ; it is followed by a second anal and two interbrachials, one at each 

 side, the latter rising almost to a level with the arm bases, and beyond the 

 upper end of the second anal. The next row generally consists of two short 

 plates, which are succeeded by numerous small, irregularly arranged, convex 

 pieces, which form a large, abruptly protruding lateral anal protuberance, 

 with the opening in the middle. First interbrachial of the regular sides 



