9 o 



NORTH AMERICAN INDEX FOSSILS. 



which occupy the same level in the adjoining tubes. Principal 



tabulae numerous, slightly arched, uniting with the incomplete one. 



In the Onondaga limestone of Michigan, Ohio and Kentucky, etc. 



Fig. 144.. Michelinia convexa (after Billings). 



102. M. favositoidea Billings. Devonic. 

 Calices 4-6 mm. in diameter ; tabulae horizontal, pores numerous, 



crowded. (Forms transition type to Favosiies.) 



In the Onondaga limestone in 

 New York, Canada, and the Falls 

 of the Ohio. 



XXXVIII. Chonostegites E. & H. 

 Coral heads composed of cylindrical 

 tubes, either closely adjoining or 

 distinct and expanding at regular 

 intervals into connecting horizontal 

 plates, which are pierced by canal- 

 like pores. Tabulae as in Michelinia, 

 septa represented by rows of spinules 

 New buds arise from the connecting plates. 



103. C. clappi E. & H. Devonic. 

 Tubes 5 mm. or more in diameter, connecting plates crowded, 



giving the whole a very compact appearance. 



In the Onondaga limestone of western New York, Ontario, and 

 Falls of the Ohio. 



Fig. 145. Chonostegites ordina- 

 tus (after Billings). 



Devonic. 



