ANTHOZOA—TETRACORALLA. 65 



with a strong epitheca. Septa numerous, radial, in several cycles 

 the larger ones reaching the center. Siluric. 



30. P. rotuloides Hall. Siluric. 

 Center with a strong depression. About 20 thick crenulated 



primary septa and an equal number of secondary ones. Base with 

 sharp costal ridges. 



In the Clinton beds of New York. 



XII. Microcyclus Meek & Worthen. 

 Disk-shaped coralla, with a flat base covered by an epitheca, 

 with numerous radiating septa and a septal fossula. Devonic. 



31. M. discus M. & W. (Fig. 98.) Devonic. 



Fig. 98. Microcyclus discus (enlarged, Fig. 99. Hadrophyllum d" 1 orbignyi (en- 

 X2). largedX2). 



Center depressed, smooth, adjoining septa uniting half way to 

 center, fossula well marked. Base flat and with a concentrically 

 striate epitheca. 



In the Hamilton beds of Canada and Illinois. 



XIII. Hadrophyllum E. & H. 

 Cushion-shaped to top-shaped coralla, the base covered by an 

 epitheca. A large cardinal fossula and two small lateral pseudo- 

 fossulae occur. Devonic. 



32. H. d'orbignyi E. & H. (Fig. 99.) Devonic. 



Flat cushion-shaped, the septa uniting before reaching center ; 

 pseudo-fossulse sometimes wanting. 



In the Onondaga beds of the Falls of the Ohio region. 



XIV. Cyathophyllum Goldfuss. 

 Corallum simple in primitive species but becoming compound in 

 more specialized types. Corallites conical, generally cylindrical in 



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