88 



NORTH AMERICAN INDEX FOSSILS. 



(The ramose or digitate varieties lead to F. radiciformis Rom.) 



95. F. placenta Rominger. Devonic. 

 Grows in broad, generally thin expansions of an undulating 



character, the base covered by a wrinkled peritheca. Calices less 

 than a millimeter in diameter with clusters of smaller ones scattered 

 about. In some specimens (especially young ones), the larger 

 tubes are circular and scattered about separately thus forming 

 transition types from F. canadensis. Tabulae of smaller tubes 

 simple, of larger, complicated with squamae. Pores uniserial. 



Abundant in the Hamilton group of Canada and Michigan — 

 also in the same formation in western New York. 



96. F. digitatus Rominger. Devonic. 

 Irregular finger-like stems, calices polygonal from one to one and 



a half millimeters in diameter. Well developed transverse squamae. 

 Abundant in the Hamilton beds of Canada, Michigan and other 

 regions. 



97. F. clausus Rom. Devonic. 

 Like the preceding, but with large round calices and small 



angular ones as in F. canadensis. The coarse thick branches of 

 this general type are F. radiciformis Rom. 



Fig. 142. Favosites limitaris (Ind. Geol. Surv. 



