6o 



NORTH AMERICAN INDEX FOSSILS. 



FlG. 88. Acrophyllum oneidaense with calyx 

 partly sectioned (Lambe). 



Regularly curved, with oblique calyx, most of the septa con- 

 verging to either cardinal or alar septa. 



Onondaga of Falls of the Ohio and other localities. 



V. Acrophyllum Thomp- 

 son & Nichols. 



Similar to ZapJirentis but 

 with the tabulae elevated 

 tent-like in the center of 

 the calyx, the septa running 

 out on them and twisted at 

 the center. Dev. 



1 8. A. oneidaense (Bill- 

 ings). (Fig. %%) 



Middle Devonic. 



Turbinate or subcylin- 

 drical, with periodic con- 

 strictions. Sides of calyx 

 nearly vertical, bottom of cup nearly half the diameter of the coral. 

 Fossula strong, extending from base of elevation to the margin 

 of the calyx. 



Onondaga limestone, Falls of Ohio, etc. 



VI. Blothrophyllum Billings. 

 Cylindrical corals, consisting of a series of invaginated cups 

 which are like that of ZapJirentis in structure, with well-developed 

 tabulae, and generally a marked fossula. Projecting margins of 

 the older cups covered by the epitheca, when not worn away. Sil.— 

 Dev. 



19. B. decorticatum Billings. Middle Devonic. 

 Large, with margins of old cups strongly projecting, generally 



denuded of epitheca. In the calyx a deep fossula and smooth 

 central space are characteristic. 



In the Onondaga limestones of Michigan, Canada and the Falls 

 of the Ohio. 



20. B. promissum Hall. (Figs. 89-90.) Middle Devonic. 

 Slender cylinders with margins of old cups generally subdued, 



the calyx with a flat central area free from septa, and no fossula. 

 In the Onondaga beds of the Falls of the Ohio. 



