600 PALAEONTOLOGY OF ILLINOIS. 



POLYPORA WHITEI Ulrich. 



PI. LXII. Fig. 2. 



Zoarium a delicate, slowly expanding, foliar net-work, branches 

 very slender, rigid, varying from 0.25 to 0.5 mm. wide, w-ith 

 nine or ten in 5 mm. Dissepiments slender, about 0.1 mm. 

 thick, enlarging at each end. Fenestrules subovate, nearly as 

 wide as the branches, 0.7 by 0.25 mm. their average dimen- 

 sions, with six in 5 mm. Zooecia in two and three rows except- 

 ing just below a bifurcation where a fourth is interpolated. 

 The ranges are separated by an interrupted or continuous 

 keel, which gives the branches so long as they have only 

 two ranges of cells, very much the appearance of a Fenestella. 

 At intervals the keel is slightly elevated so as to form a small 

 node. Apertures circular or faintly truncated at the posterior 

 side, with a thin peristome, about nineteen in 5 mm. The 

 longitudinal spaces between the apertures are equal to nearly 

 twice their diameter, and usually marked by two or three raised 

 lines. Reverse not seen. 



In this species we see, perhaps, the last of the numerous links 

 between Fenestella and Polypora. Such species have been de- 

 scribed from the Niagara and all the principal horizons between 

 that and the Hamilton group, but have not, heretofore, been 

 known from Carboniferous deposits. 



It gives me much pleasure to name this beautiful species for 

 my esteemed and distinguished friend, Dr. Charles A. White, of 

 Washington, D. C. 



Position and locality: Base of Coal Measures, Seville, 111. 



POLYPORA WHITEI var. INSCULPTA ri. var. 



PI. LXII, fig. 1. 



This variety or species closely resembles the type of P. eximia 

 but differs in the following points. The branches are slightly 

 wider, less rigid, the two ranges of zocecia sooner give way to 

 three and these to four, the separating ridges are more irregu- 

 lar, the finer lines wanting, the peristomes more elevated and 

 thicker, and the fenestrules larger, there being only 4.5 in 5 

 mm. 



Position and locality: Upper Coal Measures, at Springfield, 

 Illinois. 



