FOSSILS OF THE KEOKUK GEOUP. 495 



radials, dividing again on the sixth or eighth, beyond which 

 they are all simple ; each composed of alternating wedge- 

 si uiped pieces, which are a little wider than long, and each 

 projecting on alternate sides above for the reception of ten- 

 tacles, which are stout, angular, and composed of pieces 

 nearly twice as long as wide. 



Breadth of body, 0.55 inch ; hight to top of first radials, 

 about 0.20 inch. 



This species is remarkable for the curious rough appearance of the 

 arms, produced by tlie projection of the pieces alternately on each side, 

 and the interruption of the cariua along the dorsal side, which is not 

 continuous, but looks as if the pieces had been slipped a little alter- 

 nately to opposite sides. 



Locality and position Crawfordsville, Indiana. Keokuk division of 

 the Lower Carboniferous series. 



SCAPHIOCBTXUS McADAMSi, Worthen, Ms. 



PI. 15, Fig. 2. 



BODY below a medium size, broadly cup-shaped below 

 the top of the first radials, plates moderately thick and 

 smooth, sutures well defined. Base small, convex, about 

 half as high as wide, articulating facet for the column about 

 one-third the width of the base at its upper extremity, and 

 covered by the first joints of the column in the specimen 

 under examination. Subradials rather small, three of them 

 hexagonal, the two on the anal side larger and heptagonal. 

 First radials nearly twice as large as the subradials, width 

 greater than the hight, pentagonal and hexagonal in form. 

 Second radials higher than wide, truncated below, concave 

 011 their lateral margins, and produced into a salient angle 

 above. First anal plate nearly as large as the subradials, 

 pentagonal, and above this two more small anal plates are 

 partly visible. 



Arms rather slender, one starting from each side of the 

 second radial in the antero-lateral ravs. The arms are com- 



