23 



Position and locality. Chester limestone, near Columbia, Monroe 

 county, 111. 

 Illinois State Collection. 



POTERIOCRINUS SIMILIS. N. SP. 



Body small, basin-shaped, twice as Avide as high to the top of the 

 radial series. The plates of the body are all slightly protuberant 

 in the center, and depressed at the angles. 



Base slightly depressed and basals concealed by the first columnar 

 joints. 



Subradials about as wide as high, hexagonal and heptagonal. 



Kadials wider than high, with a w'ell-defined suture between them 

 and the brachials. Brachials on the two posterior rays, nearly three 

 times as long as wide, constricted in the middle and angular above, 

 supporting on their sloping sides the two divisions of the rays. In 

 the right antero-lateral ray, the brachial is only about twice as wide 

 as high, its upper angle projecting so as to form a short node. 



Arms two to each ray on the three rays visible, composed of 

 rounded joints, that, at first, are nearly twice as long as wide, but 

 they gradually become shorter above. They all project laterally, 

 and support strong pinnules, that are given off alternately from the 

 longest side of the arm joints. The lateral projections of the joints 

 give a zigzag arrangement to the arms. 



Only one anal plate is visible in the specimen, and this is placed, 

 as is usual in this genus, between two of the subradials, and under 

 the left side of the right posterior radial. 



Column round, and at its upper extremity composed of joints of 

 nearly equal thickness. 



This little crinoid is related to Pot. Columhiensis, from the same 

 locality, but differs from that in its more depressed base, and in the 

 slightly protuberant character of its body plates. 



Position and locality : Chester limestone, Monroe county, 111. 



Illinois State collection. 



POTERIOCRINUS POPENSIS. N. -SP. 



Body small, obconic, gradually swelling from the base to the sum- 

 mit of the radial plates, where it is about once and a half as wide as 

 long, composed of smooth, slightly protuberant plates. The basals 

 project about one-half their length beyond the column, and form a 

 low pentagonal cup, 



Subradials on the anterior side hexagonal, about as wide as long. 

 Eadials pentagonal, once and a half as Avide as long, and truncated 

 squarely across their upper margins for the reception of the brachial 

 plates. 



Brachials pentagonal, length and breadth about equal, rounded 

 externally, and sharply angular above, supporting on their sloping 

 sides the first divisions of the rays. All the arms on the anterior 

 side divide again on the seventh, eighth or ninth plate above the 



