Carboniferous Rocks of the Mississippi Valley. 307 



width of the plate. Second radial plates niucli higlier 

 than wide, strongly constricted just above the middle, en- 

 tirely separated from each other, very obtusely wedge-form 

 above, supporting on the upper faces the first arm plates. 

 First anal plate small, hexagonal ; second very small, ap- 

 parently quadrangular ; third larger than the second, form 

 not determined. 



Arms two from each ray, in the anterior ray bifurcating 

 on the eighth and tenth plate above, in the antero-lateral 

 ray bifurcating on the twelfth plate above, and in one di- 

 vision of the postero-lateral ray bifurcating on the eighth 

 plate ; simple above the first bifarcation ; composed of a 

 single series of round, short, unequal joints, which are ab- 

 ruptly thickened and projecting at the upper margins, 

 extended laterally on the long side for the attachment of 

 the tentacula, giving a peculiar zigzag appearance to the 

 arms. Tentacula long, rounded on the back, thickened at 

 the joints. 



Surface of cup marked by deeply impressed pits, ar- 

 ranged in two series ; one series at the junction of the 

 sides of the sub-radials with the points of the basal and 

 lower angle of the first radial plates ; the other series be- 

 tween the first radial plates. Column of medium size, 

 distinctly pentagonal, composed of alternating thick and 

 thinner joints, crenulated on then- surfaces. 



This is a small species of the type of P. rhombiferus, 

 Owen, (Geol. Surv. Wisconsin, Iowa, and Minnesota, pi. 

 5 D, fig. 2 ;) but differs in the less spreading cup, and in 

 the deep pits, as well as in being destitute of other sur- 

 face markings. 



Geological formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collection of C A. White. 



Scaphiocrinns ramnlosus (n. s.). Body shallow-calycu- 

 late, base small, abruptly concave, the basal plates con- 

 cealed by the summit of the column in the bottom of the 



