440 



PALEONTOLOGY OF ILLINOIS. 



Its large size, comparatively small angular cells, absence of 

 diaphragms, and very thin walls, are characters which, com- 

 bined, easily distinguish the species from others of the genus. 



Position and locality: Keokuk group, Lagrange, Mo. 



STENOPORA INTERMITTENS Ulrich. 

 \ 



Fig. 16. Sections of Stenopora inter-mittens Ulr., x!8. 



a. tangential section showing extremes in the thickness of the walls, a few perforated 

 diaphragms, and the conspicuous acanthopores ; ?>. vertical section showing the faintly 

 beaded struc ure of the walls, and the intermittent development of the acanthopores. 



Zoarium an irregular broad expansion, presenting a very 

 rough aspect. Lower side with a strong epitheca. Upper sur- 

 face very irregular in its general contour, but exhibiting faintly 

 elevated broad monticules, occupied by cells scarcely larger than 

 the average. Apertures angular, quite regularly polygonal, often 

 quadrate, between seven and eight in two mm. The zoariuin 

 seems to be composed of a number of superimposed layers. 

 The zooecial walls are very thin till near the termination of the 

 layers when they are moderately thickened, and numerous, ex- 

 ceedingly strong acanthopores are abruptly developed. Perfo- 

 rated diaphragms occur sparingly, and the walls occasionally 

 show long narrow swellings. 



The peculiar growth, thin walls, and intermittent character of 

 the zoarium, are the most marked features of the species. 



Position and locality: Keokuk group, Warsaw, 111. 



