25 



Basals extending about half their length above the first columnar 

 joints forming a low pentagonal cup. 



Subradials nearly equal in size, three hexagonal, and two on the 

 posterior side heptagonal. 



Radials four, a little wider than long, the right posterior one 

 rather narrower than the others, and all pentagonal. 



Brachials one to each ray, nearly as wide below as the radials, 

 constricted above, about once and a half as long as their greatest 

 width, sharply angular above, and supporting on their sloping sides 

 the first divisions of the arms. 



Arms composed of rounded joints, the first nearly twice as long as 

 wide, scarcely wedge-shaped below the second bifurcation, and 

 dividing the second time on the ninth plate above the brachials, 

 beyond which they continue simple, making four arms to the ray. 

 Rather stout pinnules are given off from the longest side of the arm 

 joints on alternate sides. 



The first anal plate is rather more than half the size of the sub- 

 radials, pentagonal, and rests between two of the posterior subra- 

 dials, and under the lower side of the right posterior radial plate. 

 The second and third are smaller than the first, the second resting 

 partly on the summit of the left subradial, and the third on the 

 summit of the first anal. Column unknown. 



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



Illinois State collection. 



POTEKIOCEINUS CLYTIS. N. SP. 



Body below the medium size, obconic, the basals being broken 

 away from the specimen, its relative proportions cannot be exactly 

 determined. Fragments of two of the basals that still remain at- 

 tached show that they extended beyond and above the columnar 

 facet. 



Subradials about as high as wide, three of them hexagonal, and 

 two heptagonal. 



Eadials pentagonal, somewhat irregular in size, the left posterior 

 and the left antero-lateral ones being a little larger than the others, 

 and all about once and a half as wide as long. 



Brachials one to the ray, that on the anterior ray rather the 

 longest, the others about as long as wide, constricted in the middle, 

 and sharply angular above, supporting on their sloping upper sides 

 the first arm plates. 



The arms, after their first division on the brachials, divide again 

 at unequal distances from the sixth to the tenth plate above the 

 brachials on four of the rays visible in the specimen under exam- 

 ination, beyond which they continue simple to their extremities, 

 making four arms to each ray. The arm joints are all slightly 

 wedge-formed, and quite short above the second division, and sup- 

 port strong pinnules, which are given off from the longest sides of 

 the joints. 



—4 



