604 PALAEONTOLOGY OF ILLINOIS. 



six and one-half in 1 cm., and from 0.9 to 1.3 mm. in width. 

 Dissepiments of variable width. Fenestrules oblong oval, gen- 

 erally a little narrower than the branches, and three or four 

 times longer than wide, usually 2.4 by 0.7 mm. and 3.5 in 1 

 cm. Zooecia in from five to eight ranges. Apertures circular, 

 arranged in more or less regular diagonally intersecting series, 

 in which four occur .in the space of 1 mm. Longitudinally 

 about eleven in 3 mm. The zooecia apertures usually do not 

 extend to the margin of the branches. 



The specimen for which the above name is provisionally pro- 

 posed, is not sufficiently preserved to render its specific deter- 

 mination satisfactory. It is proportionately larger than P. cor- 

 ticosa. The P. koninckiana, lately described by Waagen and 

 Pichl from the Permo-carboniferous deposits of India, agrees in 

 many respects, but I do not believe them identical. Better speci- 

 mens of the American form are necessary before its affinities 

 can be ascertained. 



Position and locality: Upper Coal Measures, Sugar Creek, 

 Sangamon county, Illinois. 



FENESTRALIA Prout, 1859. 



(Trans. St. Louis Acad. Sci. Vol. I, p. 235.) 

 (For generic diagnosis see page 396.) 



The validity of this genus is provisionally admitted because 

 of the importance of the carina among the FEXESTELLID.E. Be- 

 yond this feature, F. sancti-ludovici differs in no respect from 

 Polypora, unless we credit the fact that the rows of cells are 

 constantly four, with generic importance. 



FENESTRALIA SANCTI-LUDOVICI Prout. 



PL LV, fig. 5. 



Fenestralia St. Ludovici Prout, 1859. Trans. St. Louis Acad. Nat. Sci. Vol. I, p. 

 235, PL 15, figs. 1-la. 



Zoarium a large flabelliform expansion. Branches 9.5 to 11.5 

 in 1 cm., rather slender and unequal, somewhat rigid, strongly 

 carinated, the aperture bearing surfaces either flat or slightly 

 convex; average width of branches 0.6 mm., increasing from 



