INVEKTEBKATES. 315 



openings and the central spine on two of the rays. Arm openings 



two to each ray. Arms and column unknown. 

 This species is related to T. sexlobatus, (Shumard's sp.) but differs 



from that in its more symmetrical form, its less protuberant radial 



and anal plates, and less nodose summit. 



Position and locality : Chester, limestone, Monroe county, Illinois- 

 No. 2,453, Illinois State collection. 



GENUS AGASSIZOCRI^TUS, Troost. 

 AGASSIZOCKINUS PAPILLATUS, Worthen. 



PI. XXIX, Fig. 17. 



Agassizocrinus papillatus, WOBTHEN, Feb., 1882. 



Bulletin No. 1, of the Illinois State Museum of Natural History, p. 36. 



Body rather below the medium size, subovate, width at the sum- 

 mit of the radials a little more than the length, composed of mas- 

 sive, slightly rounded plates that are separated by well-defined and 

 deep sutures. 



Basals pentangular, about as wide as long, and rounded below, 

 where their inner margins form the walls of a very small pentapet- 

 alous opening for the attachment of a very delicate round column, 

 two or three joints of which remain attached to one of our speci- 

 mens. 



Subradials, three hexagonal, counting three angles below, and two 

 on the posterior side heptagonal, length and breadth about equal. 



Kadials pentangular, nearly twice as wide as long, except the two 

 posterior ones, which are rather narrower than the others. 



Brachials about the same size and form as the radials. and sup- 

 port on their upper sloping sides the first arm plates. Arms two to 

 each ray, composed of quadrangular joints that gradually diminish 

 in width to their extremities. 



Anals, three visible ; the first is nearly as large as the radial 

 plates, pentagonal and situated as in Poteriocrinus, between two of 

 the subradials, and partly under the left side of the right posterior 

 radial. The second is about half as large as the first, and rests on 

 the upper truncated margin of the left posterior subradial. The 

 third is very small, and rests upon the upper angle of the first 

 anal. 



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



No. 2,444, Illinois State collection. 



