300 PALEONTOLOGY OF ILLINOIS. 



cates the second time on the eight or ninth plate, the right branch 

 sending off two additional arms on the seventh, and again on the 

 fourteenth plate, while the left branch gives off another arm on the 

 eighth or ninth plate, beyond which it is not preserved. There are 

 probably eight arms to this ray. The other rays are not preserved 

 beyond the second bifurcation. The arms are composed of rather 

 short, wedge-formed joints, that give off strong pinnules from their 

 longest sides. 



Anal area unknown. Column round, composed at first of rather 

 even joints, with a thicker one intercalated at short intervals below. 

 The calyx of this species could not be readily distinguished from 

 several others that are found in the Chester limestone, but its long, 

 slender arms, and their mode of bifurcation, are its distinctive 

 characters. 



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



No. 2,437, Illinois State collection. 



POTERIOCRINUS KASKASKIENSIS, Worthen. 



PL XXIX, Fig. 15. 



Poteriocrlnus Kashas kiens is, WORTHEN, Feb., 1882. 

 Bulletin No. 1, of the Illinois State Museum of Natural History, p. 27. 



Body small, bell-shaped, nearly twice as wide as long to the sum- 

 mit of the radials, composed of rather thin, smooth plates, so closely 

 anchylosed together that their relative size and form cannot be deter- 

 mined. The radials are nearly as long as wide, pentagonal, thick- 

 ened on their upper margins with a lip-like suture between them 

 and the first brachial plates. 



Brachials two, the first quadrangular, the second pentagonal ; 

 length and breadth about equal, both rounded externally, and con- 

 stricted, the second sharply angular above, and supporting on its 

 sloping sides the first divisions of the rays. 



Arms composed of rather long, wedge-shaped joints, that project 

 slightly on their outer margins, giving them a somewhat zigzag 

 appearance, and after their first division on the second brachials they 

 all divide again on the eighth to the tenth plate above the brachials, 

 giving four arms to each ray as the normal number. In one of our 

 specimens, however, one arm gives off a branch near its extremity, 

 making five arms to that ray. 



Pinnules rather strong and attached to the longest side of the arm 

 plates. Anal plates unknown. Ventral tube cylindrical, and about 

 twice the diameter of the adjacent arms. 



