596 PALEONTOLOGY OF ILLINOIS. 



Zooecia normally in three or four, somewhat irregular, alterna- 

 ting ranges, just before bifurcation in five or six, and immedi- 

 ately after, rarely in two, generally in three. Apertures small, 

 circular, when perfect somewhat pustuloid, about twenty-five in 5 

 mm. On the reverse the branches are rather narrowly rounded, 

 slightly zigzag, and smooth or finely striated; the dissepiments 

 scarcely depressed, and a little wider than on the opposite face; 

 the fenestrules about as wide as the branches, and of oblong 

 subquadrangular or subovate form. A few root-like apendages 

 spring from the branches near the base, and occasionally fap- 

 ther up on the frond. 



This species is on the order of, but in every way smaller than 

 P. cestriensis. It has been erroneously identified in the Scotch 

 Carboniferous shales by Mr. John Young. Mr. G. R. Vine,* 

 after noting the resemblances and differences comes to the same 

 conclusion, although his American examples of the species, are, 

 as I have good reason to know, really quite different from 

 Front's P. tuberculata, and probably belong to P. spinulifera 

 of this work. The slightly raised keel which Prout says separ- 

 ates the rows of cells in this species I have never seen, nor 

 are the tuberculations so numerous as stated by him. These 

 characters he probably obtained through confounding a frag- 

 ment of P. cestriensis with the true P. tuberculata. His fig- 

 ure is quite reliable and shows the tubercles as above described, 

 but no lines between the rows of cells. The dissepiments are 

 represented a little too thin. 



Position and locality: Chester group. Not uncommon at 

 Chester, 111.; rare at Litchfield, Ky. 



POLYPORA CORTICOSA UMch. 



PL LX, Figs. 5-5c, and PL LXI, Fig. 1. 



Zoarium rather small, forming a flattened expansion, perhaps 

 not exceeding three or four cm. in height, which springs from 

 a strong, solid, finely striated foot-stalk. Both surfaces of the 

 branches near the base are covered with the striated deposit, 

 causing the fenestrules to become very small or entirely filled 



* Notes on Yoredale Polyzoa, 1886, p. 17. 



