420 PALAEONTOLOGY OF ILLINOIS. 



marked by depressions, which seem to have resulted from 

 abortive cells larger than those which formed the radiating 

 striae. As the annulations become more prominent toward the 

 border, the striations become less distinct and more irregular. 

 Chalices only seen upon the upper face by grinding the 

 lower surface, where they appear to be round or subprismatic, 

 longer than broad, vertical in direction, alternately juxtaposed 

 in radiating lines, with no sheaths distinct from the plexiform 

 interchalicular spaces, which are formed by the union of minute 

 cells, varying in size and development. 



A careless observer might refer this species to the genus Fungia, as in 

 general appearance it resembles very closely some of the discoidal forms of this 

 coral, more particularly the Fungia discoidea, Gold., tab. xiv, fig. 9 a. But a 

 minute examination of its structure renders it manifest that it is a true 

 polyzoan, allied somewhat to Ceriopora (Gold.) The chalices and the inter- 

 chalicular spaces are not septate, for we have found on careful examination 

 that the septa in the forms submitted to examination are more imaginary than 

 real, being caused by the breaking in of cells forming a part of the net-like 

 interchalicular spaces. 



Geological position and locality : Keokuk group, St. Francisville, Mo. 



Ctclopora discoidea, Prout. 



PI. 22, fig. 10. 

 Cyclopora discoidea, Prout, 1860. Proceed. St. Louis Acad. Sci., vol. 1, p. 578. 



Polyzoum a flattened subconcave or subconvex expansion, 

 with a central elevation ; discoidal portion about two or two 

 and a half inches wide, with radiations distinctly marked, 

 showing the bases of the chalices on the upper surface in con- 

 nected lines and alternate series. Margin irregular, running 

 into irregular frondescent expansions, which still preserve the 

 concentric form of the banded sole. One specimen is so deeply 

 concave as to become infundibuliform ; chalices only on one 

 side, larger and not so long as in C. fungia. 



Geological position and locality : Keokuk group, Warsaw, Illinois. 



