602 PALEONTOLOGY OF ILLINOIS. 



POLYPORA SUBMARGINATA Meek. 



PI. LXI. flg. 6-6b. 



Polypora marginata Geinitz, 1866. Garb. u. Dyas in Neb. p. 69, PL 5, figs, 11, a, b, 

 and 12 a, b. (not McCoy. 1844, Syn. Carb. Foss. Ireland p. 206, PL 29, flg. 5.) 

 Polypora submarginata Meek, 1871. Pal. E. Neb. p. 154, PL 7, flgs. 7a, 7b. 



Zoarium flabelliform, probably not exceeding three or four 

 cm. in height. Branches about seven in 1 cm., sub-pentagonal 

 in cross section, with the obverse side strongly convex, subcar- 

 inate when typical, and carrying a row of small, conical, rather 

 prominent spines or tubercles along the middle, about 0.3 mm. 

 apart; the two lateral margins sharply angular. The average 

 width of the branches is about 0.7 mm., but gradually increases 

 from 0.5 mm. to 1.0 mm. between the bifurcations. Dissepi- 

 ments rather long, slender, 0.3 to 0.5 mm. wide, spreading 

 slightly at each end, faintly striated or smooth, narrowly 

 rounded. Fenestrules oblong oval to subquadrangular, about 

 as wide as the branches, twice as long, averaging 1.7 by 0.8 

 mm., and 4 to 4.5 in 1 cm. Zocecia five or six to the fenestrule 

 generally in five ranges, which number may be increased to six 

 just before bifurcation. Immediately after, but only for a short 

 distance, there are only three or four ranges. Apertures circu- 

 lar, 0.11 mm. in diameter, nearly twice their diameter apart 

 longitudinally, about fifteen in 5 mm., rather irregularly ar- 

 ranged, with a well developed but not strong peristome. In a 

 normal development the apertures of the central range alter- 

 nate with the tubercles. On the reverse the branches are nar- 

 rowly rounded, flattened on the sides, and smooth or finely 

 striated. Near the base they are irregular, the dissepiments 

 nearly as strong and on a level with the branches. The fenes- 

 trules are large, oblong subquadrate, or irregular. 



This distinct and common species is very characteristic of the 

 Upper Coal Measures of the western states. It is on the order 

 of, but much larger than the P. nodocariiiata. Associated with 

 it in Illinois, I have met with a smaller species having no 

 tubercles and 5.5 fenestrules to 1 cm. The. latter also occurs 

 in the Lower Coal Measures, from which I have obtained good 

 specimens. These have fine waving ridges between the rows of 

 cell apertures, agreeing in this and other respects rather closely 

 with McCoy's P. marginata. 



