LNVEETEBEATES. 517 



on the outside ; third radials about as high as the first, four iu number 

 and giving support on their upper sloping angles to two arms that con- 

 tinue single to their extremities. The middle ray on the anterior side 

 gives oft" a single arm from the summit of the first radial piece, which, 

 like the others, continues simple to its extremity. First anal plate hex- 

 agonal, about as large as the subradials, upon the upper angles of which 

 it rests, and supporting two smaller plates above, which are succeeded 

 by others still smaller that exteud up to the base of the ventral tube. 

 Ventral tube composed of very small plates, and strongly inflated at 

 the summit, with a well-marked anal opening on its anterior side about 

 half an inch above its lower extremity. The plates surrounding this 

 opening form a prominent projecting rim, such as may be seen around 

 this opening in the criuoids where it is located on the side of the body 

 as in Agaricocrinus Americanus, and many others. This character may 

 also be seen more distinctly expressed in the example of Scaphiocrinus 

 uncus, figure 1 of the same plate. 



This species is nearly related to P. Lulianensis, M. and W., Vol. 1IT, 

 Geological Survey of Illinois, p. 515, PI. 20, fig. 4, but differs from that 

 in the form and proportion of its body plates, and in the number and 

 arrangement of its arms. 



Position and locality: Crawfordsville, Indiana, in shales belonging to 

 the Keokuk group, Lower Carboniferous. 



This species is dedicated to Mr. L. W. Corey, of Crawfordsville, 

 Indiana, from whom the typical specimen was received. Eor the speci- 

 men showing the ventral tube, I am indebted to Prof. E. O. Hoyey, of 

 Wabash College. 



PoTEEioCErNUS Van Hoknei, Worthen. 



PI. 31, Fi£. 2,3. 



Body obconical below the arms, surface smooth ; basal plates pentag- 

 onal as seen beyond the facet for the reception of the column, a little 

 wider than long and uuiting to form a shallow cup; subradials, three 

 pentagonal and two hexagonal, length and breadth about equal ; first 

 radials nearly once and a half as wide as long, pentagonal and a little 

 concave on their upper margins so as to leave a suture between that and 

 the second radial plate ; second radials on the anal side nearly 

 twice as long as wide, strongly rounded and constricted in the middle 

 and supporting the arms on their superior sloping angles. Arms, two 

 to each ray, as far as can be seen on our specimens, composed of smooth 

 wedge-formed pieces, and apparently continuing single to their extrem- 

 ities. Anal plates, seven or eight visible, the two lowest less than half 

 the size of the subradials, pentagonal, and resting on the upper mar- 



