INVERTEBRATES. 



343 



GENUS ACKOCKLNTJS, Yandell. 

 ACROCKINUS WORTHENI, Wachsmuth. 



PI. XXX, Fig. 13. 



Acrocrinus Wortheni, WACHSMUTH, February, 1882. 

 Bulletin No. 1, of the Illinois State Museum of Natural History, p. 40. 



Anal plates. 

 Diagram illustrating the structure of the genus Acrocrinus. 



This species is described from a single specimen, of which only 

 the calyx is preserved ; the vault, the arms and the columns are so 

 far unknown. The calyx, however, is in excellent preservation, and, 

 notwithstanding its small size, exposes plainly every plate. The 

 form is calyculate, broadly truncate at the bottom, abruptly bending 

 upward toward the base of the first radials, whence it gradually 

 decreases in width to the arms. Its length is 40.100 of an inch, 

 its greates width 42.100, the width at the arm bases 34.100. The 

 plates are plain, without ornamentation, but sufficiently convex to 

 point out the sutures. 



