Escharopoa.] 



Genus ESCHAROPORA, Hall. 



Escharopora, Hall, 1847. Pal. N. Y., vol. i, p. 72. 

 Ptilodictya (part.), Uleich and many other authors. 



Zoaria bifoliate, simple or branching, pointed below, and articulating into 

 a'spreading base as in Ptilodictya. Zooecia arranged in regular diagonally intersect- 

 ing series throughout. In the small species these rows extend in a continuous line 

 across the fronds, but in the larger forms their course is interrupted at more or less 

 regular intervals by the development of raised clusters of large cells. Apertures 

 rounded, elliptical or subcircular, set into sloping areas ; the latter generally of 

 rhomboidal or hexagonal shape and sharply defined, in other cases longitudinally 

 confluent, and connected by a narrow channel. 



Internal structure essentially as in Ptilodictya, the differences chiefly due 

 to the different zooecial arrangements. 



Type : . E. recta Hall, Pal. N. T., vol. i, p. 72 ; 1847. 



Better known examples are Ptilodictya falciformis Nicholson, Pal. Ohio, vol. ii, p. 

 259, 1875, and P. pavonia d'Orbigny, Prodr. de Pal., vol. i, p. 22, 1850. 



CLASSIFICATION OF SPECIES. 



Section a ; zoaria simple, without monticules. 



E. acuminata (James), Galena limestone, Iowa ; Utica horizon of the Cincinnati group, Ohio and 



Kentucky. 

 E. annularis, n. sp., lower Trenton, Minnesota. 



E. falciformis (Nicholson), Cincinnati group, Ohio, Indiana, Kentucky. 

 E. recta Hall, Trenton limestone. New York, Canada, ? Galena shales, Minnesota. 

 E. subrecta (Ulrich) lower Trenton shales, Minnesota. 



Section b ; zoaria simple, with monticules. 



E. hilli (James, as figured by Ulrich), Cincinnati group, Kentucky. 

 ' E. libana (SafEord), Birdseye limestone, Kentucky, Tennessee. 

 E. maculata (Ulrich), Cincinnati group, Ohio, Kentucky. 

 J7. pavoraia (d'Orbigny), Cincinnati group, Ohio, Indiana, Kentucky. 

 E. n. sp., Birdseye limestone, Tennessee. 

 E. n. sp. [near pavonia), top of Trenton, Nashville, Tennessee. 

 E. n. sp., Cincinnati group, Kentucky. 



Section c ; zoaria branching. 



E. briareus (Ulrich), Birdseye limestone, Tennessee. 

 E. confluens, n. sp., lower Trenton shales, Minnesota, Tennessee. 

 E. ramosa (Ulrich), Birdseye limestone, Tennessee, Kentucky. 

 E. n.sp., Utica horizon of the Cincinnati group, Kentucky. 



From the preceding classiflcations we learn that Escharopora began in the 

 " Birdseye " or earlier, and ceased apparently in the age of the Cincinnati group — 

 strictly speaking, in the middle division of that formation. True Ptilodictya is first 

 met with in the upper beds of that group of rocks, and continues with varying rep- 

 resentation up into the Lower Devonian. 



