676 PALAEONTOLOGY OF ILLINOIS. 



at irregular intervals, consisting of clusters of mesopores. Zo- 

 oecia apertures obscured by the projecting acanthopores, sub- 

 angular, 0.15 mm. in diameter, with those in the immediate 

 vicinity of the "maculae" of much larger size, the largest being 

 about 0.28 mm. in diameter. The arrangement is in irregular 

 series with nine or ten of those in the intermacular spaces in 2 

 mm. Mesopores numerous, of unequal sizes, irregularly distri- 

 buted, never isolating the zocecia, and much obscured by the 

 acanthopores. The latter are large and slightly exceed the zo- 

 oecia in number. 



From thin sections we learn that the zocecia are at first pros- 

 trate and thin-walled, then bending abruptly proceed direct to the 

 surface. The walls become thickened and apparently amalga- 

 mated, the mesopores and acanthopores are developed, and, at 

 intervals of about 0.1 mm., several superior hemisepta will be 

 seen, in vertical sections, to project from the posterior wall into 

 the zooecial cavity. The cavity of the acanthopores is compara- 

 tively large and crossed by closely set, delicate diaphragms; 

 their walls are composed of obliquely laminated tissue. The 

 mesopores appear largely filled by a structureless deposit in 

 which an occasional diaphragm may be detected. 



When the under surface alone is visible the species might be 

 confounded with Proutella discoidea. A little moisture applied 

 to the epitheca will show that that species has larger cells, the 

 radiating lines being farther apart. The under surface of Cyclo- 

 pora fungia is strongly wrinkled; that of Cycloporella? perversa 

 even more so. 



Position and locality: Keokuk group, Warsaw, 111. 



CYCLOPORELLA ? PERVERSA Ulrich. 



PI. LXIX. flgs. 5-3b. 



Zoarium a free or parasitically attached, thin, irregular ex- 

 pansion, 8 to 10 cms. in diameter, and from 0.5 to 2.0 mm. in 

 thickness, being often composed of two or three superimposed 

 layers. When free the lower surface is strongly wrinkled, the 

 zoarium appearing sometimes like a crumpled piece of cloth. 

 Zooecial tubes with a short prostrate region, bending soon to 

 proceed direct to the surface; intersected by one or two dia- 

 phragms in each layer. Walls moderately thickened, composed, 



