442 PALEONTOLOGY OF ILLINOIS. 



Position and locality: Chester group, Chester and numerous 

 other localities in Illinois; also common in the Warsaw beds, 

 which furnished the original examples of the species, and in the 

 St. Louis limestone. 



STENOPOEA CESTRIENSIS Ulrich. 



PI. LXXIV, flg. 7,7a. 



Zoarium forming laminar expansions of considerable breadth, 

 the under surface provided with a thick concentrically wrinkled 

 epitheca. The typical example consists of but a single layer 

 with an average thickness of about five mm. Celluliferous surface 

 spinulose where well preserved, with low broad tubercles occu- 

 pied by cell apertures slightly larger than the average; cen- 

 ters of monticules three or four mm. apart. Zocecial aper- 

 tures sub-circular or polygonal, about eleven in three mm. Im- 

 mature portion of zocecial tubes short, prostrate, bending 

 rather quickly and proceeding direct to the surface. Walls 

 thickened, but seldom appearing distinctly moniliforrn, the 

 swellings usually being merged into each other. Divisional line 

 between zocecia sharply defined. Mesopores probably absent. 

 Diaphragms abundant, close set, five or six in one mm. Cen- 

 tral perforation large, often closed with a flat or concave plate. 

 Acanthopores numerous, rather large, usually situated at the 

 angles and bulging a little into the zocecial cavity. They ap- 

 pear more than usually conspicuous in tangential sections, being 

 sharply defined and the dark central spot comparatively large. 



This species is related to S. tuberculata Prout, but the cells 

 are smaller, their individual walls more clearly defined, the 

 acanthopores more conspicuous, and the zooecial layers at least 

 twice as thick. 



Position and locality: Chester group, Chester, 111. 



STENOPORA RAMOSA Ulrich. 



PI. LXXIII, flg. 6, 6c. 



Zoarium ramose, consisting of cylindrical or somewhat com- 

 pressed stems from five to ten mm. in diameter. Surface usu- 

 ally even but marked with clusters of cells a little larger than 



