612 PALEONTOLOGY OF ILLINOIS. 



enclose a faintly margined circular suboval depression. At the 

 bottom of this depression (which with the aperture resembles 

 the figure 8), I have in several instances detected a small pore. 

 Reverse convex, appearing smooth under the ordinary hand 

 lens. 



This interesting species brings to mind several chilostomatous 

 Bryozoa, but, for the present at least, is fittingly referred to 

 Thamniscus. The superficial character of the zocecia, in fact, 

 the whole obverse face of the zoarium is quite different from 

 that of the ordinary species of the genus, making detailed com- 

 parisons unnecessary. 



Position and locality: Upper Coal Measures; Greenwood Co., 

 Kansas. 



PHYLLOPORA King, 1849. 



(Mon. Permian Fos. England, p. 40.) 

 (For generic diagnosis see page 397.) 



The characters of this genus, as determined by an examina- 

 tion of P. ehrenbergi King, the type of the genus, place it in 

 the immediate neighborhood of Polypora. In its zooecial charac- 

 ters the type species agrees thoroughly with Polypora, the 

 most important difference between the two genera being that, 

 while in the latter, the branches are approximately straight 

 and united to each other by rythmically developed non-porifer- 

 ous bars, called dissepiments, they unite by inosculation to 

 form a regular round or oval-meshed network in Phyllopora. 

 The earliest true Phyllopora known to me is from the Upper 

 Helderberg group, and is next described under the name of P. 

 aspera. The Silurian Retepora species which I and others have 

 placed in this genus, are now known to possess very different 

 zocecia, and must be referred elsewhere, but mainly to the new 

 genus Phylloporina. 



In American rocks true species of Phyllopora are very rare, 

 and up to this time I have met with only two undoubted 

 species, both of which are here described. A somewhat doubtful 

 third form is partially illustrated on plate LV. It agrees with 

 P. superba in having sub-rhomboidal fenestrules on the reverse, 



