586 PALEONTOLOGY OF ILLINOIS. 



POLYPORA SHUMARDI PrOUt. 



PI. LV, figs. 2-2d. 



Polypora shumardi Prout, 1859. Trans. St. Louis Acad. Sci. Vol. 1, p. 271. PI. 16. 



fig. 3-3b. 



Polypora shumardi Hall, 1885. Bept. State Geol. for 1884, p. 35 PI. 1, flg. 5. 

 Fenestella cultellata Hall, 1881. Trans. Alb. Inst. Vol. X. Abstract p. 21. 



Fenestella (Polypora) cultellata Hall, 1883. Rept. State Geol. for 1882. Explanation to 



PI. 29. 



Fenestella cultellata Hall. 1886. Eept. State Geol. for 1885. Explanation to PI. 41. 

 Fenestella cultellata Hall, 1887. Pal. N. T. Vol. 6, p. 160. 



Zoarium a large irregular fan-shaped expansion, the largest 

 fragment seen being over 10 cm. high, and 12 cm. wide. Near 

 the base and along the free margins there are, usually, strong 

 root-like processes which may be attached to foreign bodies. 

 Branches rather strong and straight, subangular, varying from 

 0.6 to 1.0 mm. in width, with eight or nine in 'one cm.; along 

 the middle, on well preserved examples, with a series of elong- 

 ate, strongly projecting, sharp, elevations or spines, about one 

 to each fenestrule. Dissepiments half the width of the branches, 

 depressed, rounded, often with a sharply margined irregular ex- 

 cavation or channel. Fenestrules narrow, elliptical, eight or 

 nine in 1 cm. Zocecia generally in four or five alternating long- 

 itudinal ranges, increasing to six or seven before bifurcation; 

 about seventeen in 5 mm. Apertures circular, rather large, 

 regularly and closely arranged, the not very well developed 

 peristomes being almost in contact laterally. On the reverse 

 the branches and dissepiments are rounded, commonly smooth, 

 nearly on the same plane, the latter expanded at their junction 

 with the former and about 0.6 mm. in length. 



A very abundant and easily recognized species. Some of the 

 silicified examples show the superior hemiseptum very clearly as a 

 narrow crescentic plate projecting obliquely downward and forward 

 from the posterior basal margin of the "vestibule." Other speci- 

 mens have the superficial aperture closed by the usual opercular 

 plate, the small perforation of which may be open or closed by 

 a round stopper. 



Position and locality: Upper Helderberg group. Falls of the 

 Ohio, and Utica, Indiana. 



