500 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



the arm regions and the summit of the posterior oral is pierced by the anal 

 opening. Orals in contact laterally, large and highly convex ; the posterior 

 one twice as large as the smaller orals, or larger and equally tumid. 



Horizon and Locallti/. — Keokuk group ; Keokuk, Iowa ; Barren and 

 Metcalf Cos., Ky. ; White's creek near Nashville, Tenn., and Indian creek, 

 Montgomery Co., Ind. 



Ti/pes in Professor Wetherby's collection. 



Remarks. — This species is readily recognized by its stellate form, the 

 very slight concavity of the dorsal cup, and by the form and arrangement of 

 the plates. 



Agaricocrinus elegans Wetheeby. 

 Plate XL. Figs. Sa, h. 



1881. Wetheebt; Journ. Cincin. Soc. Nat. Hist., Vol. IV., p. 179, Plate 5, Figs, i, ia, b. 

 1885. W. and Sp. ; Revision Palffiocr., Part HI., p. 106. 



Nearest to A. crassus, but smaller and less robust. Calyx depressed, 

 pentalobate in a dorsal aspect, wdth rather deep recesses between the 

 rays ; the base moderately excavated. Plates of the dorsal cuji slightly 

 tumid, basals and radials excepted ; the principal plates of the ventral 

 disk highly convex. 



Basals hidden by the column. Radials smaller than the costals. First 

 costals quadrangular, hexangular or heptangular, as wide as long ; the sec- 

 ond costals wider than the first, and about as long. First distichals axillary 

 in one or both divisions of the posterior rays, supporting 2X2 moderately 

 large palmars ; the other rays have two successive distichals, which interlock 

 ■with those of opposite series, and with the arm plates above. Arm facets 

 tending slightly upward, confluent to the second arm plates. Arms three to 

 four in the posterior rays, and two hi the other rays. First interbrachials 

 comparatively short, generally rising to the first costals, sometimes to the 

 second. The plates of the second row long, reaching to near a level with 

 the arm openings ; they support a row of three or four smaller plates, which 

 are partly interbrachial, partly interambulacral. Anal area extremely wide ; 

 the first plate narrower than the radials, and but very little longer, the three 

 succeeding ones almost as large ; the latter support three smaller plates, and 

 these numerous other plates, which form together a longitudinal, slightly 

 elevated ridge, which at half way to the orals is pierced by the anus. Ven- 

 tral disk pyramidal. Orals large and highly convex, the posterior one in 



