508 THE CEINOIDEA CAMEEATA OF NOETH AMEEICA. 



Agaricocrinus stellatus Hall. 

 Flate XXX7IIL Figs. 7a^e. 



1858. Hall ; Geol. Rep. Iowa, Vol. I., Part II., p. 56i. 

 1881. W. aud Sp. ; RevisioE Palaiocr., Part II., p. 113. 



Sjn, Agaricocrinus geometricus Hall ; 1860, Suppl. Geol. Eep. Iowa, p. 56. 



A small species, resembling A. Mlairema in the form of the dorsal cup, 

 and A. hillatus in the construction of the tegmen. Calyx subpyramidal, 

 wider than high, and distinctly pentangular across the arm facets, the sides 

 a little constricted. Lower face of the dorsal cup somewhat convex, the 

 basals and radials a little concave, or the radials stretched out horizontally 

 and only the basals depressed. Plates flat, with shallow grooves along the 

 suture lines. 



Basals sometimes extending beyond the column. Radials about as wide as 

 long, the upper face twice as wide as the lower. First costals a little smaller 

 than the radials, quadrangular, wider than long, and the upper face wider 

 than the lower. Second costals pentangular, exceptionally hexangular or hep- 

 tangular, generally a little wider than the first. Distichals 2X2 in the calyx ; 

 the upper one followed by two series of free brachials. Arm facets large, 

 directed horizontally or nearly so ; those of the same ray forming an angle 

 of 60°. Arms ten, stout, gradually tapering, and composed of rather long 

 joints. Interbrachials one and two ; the first rising generally to the top of 

 the first distichals ; the two of the second row, which are narrow and long, 

 come to a level with the arm openings. First anal much longer than the 

 radials, followed by two rows of three plates. The upper part of the anal 

 area is composed of irregular pieces forming a well defined ridge, which 

 near its upper end contains the anus. Posterior oral large and spinous, 

 the four others and the radial dome plates highly convex ; interambulacral 

 pieces almost flat. 



Horizon and Locality. — Lower layers of the Upper Bui'lington limestone; 

 Burlington, Iowa, and at several places in Illinois and Missouri. 



Tt/2oe in the (Worthen) Illinois State collection, Springfield. 



Agaricocrinus convexus (Hall) W. and Sp. 

 Plate XXXVIII. Figs, la, h. 



1860. Agarieocrimis pentacjonus. Tar. convexus — Hall ; Suppl. Geol. Rep. Iowa, p. 58. 

 1361. Agaricocrinus convexus — W. and Sp.; Revision Palseocr., Part II., p. 113. 



