166 CRINOIDS. 



Amphoracrinus divergens (Hall). 



Plate xxii, fig. 4. 



Adinocrinus divergens Hall, 1860 : Geol. Iowa, vol. I, Supp., p. 36. 

 Actinocrinus planobasalis Hall, 1860: Geol. Iowa, vol. 1, Supp., p. 19, pi. 



iv, figs. 10-11, 

 Actinocrinus quadinspinus White, 1862: Proc. Boston Soc. Nat. Hist., 



vol. IX, p. 15. 

 Amphoracrinus divergens Meek & Worthen, 1873: Geol. Sur. Illinois, vol. 



V,p. 3S8. 

 Amphoracrinus multiramosus Meek & Worthen, 1873: Geol. Sur. Illinois, 



vol. V, p. 389, pi. vi, figs. 6, 6a-c. 



Calyx rather higher than wide, strongly pentalobate ; 

 dorsal cup very shallow ; ventral side greatly elevated or in- 

 flated, with a short, subcentral anal tube. Column circular, 

 with a very small axial canal. Basals three, of medium size, 

 forming a small six-sided disk, and with a slight circular eleva- 

 tion around the stem juncture. Eadials considerably wider than 

 high; costals short and broad; distichals somewhat smaller. 

 Arms stout, bifurcating. Interradials usually three in number, 

 rather small. Orals conspicuous, bearing large spines. Surface 

 marked by small pustules and indistinct, irregular wrinkles. 



Horizon and localities . — Lower Carboniferous, lower 

 Burlington limestone : Louisiana. 



Genus Agaricocrinus Troost. 



Calyx more or less distinctly pyramidal and pentalobate, 

 usually somewhat wider than high ; dorsum discoid, concave 

 centrally ; vault high, inflated, prominently nodose. Basals 

 three, small, subequal. Eadials small, hexagonal. Costals 

 2x5; first quadrangular, rather small; second large, broadly 

 pentagonal ; distichals large, wide ; other brachials very wide, 

 short, interlocking, the lower few more or less cuneate. Arms 

 stout, long; pinnules slender. Dorsal interradials elongate, 

 the first large, obovate; the two in the next row very narrow. 

 Anal plate similar to the radials, but somewhat larger; fol- 

 lowed by three large ossicles in the second row, and these 

 succeeded by smaller pieces. Ventral plates large, tuberculose, 

 central one prominent. Column round; nodal pieces larger 

 and thicker than the othero and with regularly rounded margins. 



