Carboniferous Rocks of the Mississippi Valley. 301 



marked by lines which form a star, the rays equalling in 

 number the sides of the plate, across which they join those 

 of the adjacent plates. 



Geological formation and locality. Burlington lime- 

 stone, Bm-lington, Iowa. Collections of Dr. O. Thieme 

 and C. A. White. 



Poteriocrinus ventricosus (n. s.). Body broadly calycu- 

 late. Basal plates of medium size, projecting above the 

 top of the column in a low coronated cup with five salient 

 angles. Sub-radial plates hexagonal, one heptagonal ad- 

 joining the anal series, little wider than high. First radial 

 plates proportionally large, irregularly pentagonal, having 

 the upper portions of the lateral sides deeply inflected. 

 Second radial plates smaller than the first, entirely sepa- 

 rated from each other at their lateral margins, pentagonal 

 and obtusely wedge-form above, supporting on their up- 

 per sides the first plates of the free arms. Anal plates of 

 medium size ; first one somewhat regularly pentagonal ; 

 second elongate, hexagonal, larger than the first ; the re- 

 mainder not determinable. 



Arms two from each ray, bifurcating at the sixth or 

 eighth plate from their base ; the outer branch again bi- 

 furcating two or three times at irregular distances above ; 

 composed in the lower part of a single series of short, 

 broad plates, alternately longer and shorter on the oppo- 

 site sides, in the upper part becoming attenuated on the 

 short side so as to allow the plate above and the plate be- 

 low to join at the thicker margin. 



Proboscis large and inflated in the upper part, reaching 

 to near the extremities of the arms, composed of numer- 

 ous polygonal plates. The plates of the summit smaller 

 than the body plates, ornamented by numerous pointed 

 nodes arranged so as to form a star on each plate. 



Column strong, round, composed of short plates of une- 

 qual thickness. 



