120 



NORTH AMERICAN INDEX FOSSILS. 



13. D. flabellata Ulrich. (Fig. 178,/) Ordovicic. 



Flabellate or fan-shaped expansion, minute with distant, tubular 

 cells projecting obliquely. • 



Trenton of Minnesota. 



IX. Hederella Hall. 

 Adhering zoaria with the tubular cells given off on alternate 



Devonic. 

 (Fig. 179, a, b.) 



sides from central tubular axis. 



14. H. canadensis (Nicholson). 



Profusely branching, with 

 long, slender zocecial tubes with 

 oval apertures. 



Hamilton group of New York, 

 Ontario, Falls of the Ohio and 

 Upper Canada; Onondaga of 

 Ontario. 



X. Hernodia Hall. 

 Similar to preceding, but later 

 zocecia budding from preceding 

 ones. Devonic. 



15. H. humifusa Hall. 



Devonic. 



Cells 5 mm. long, gradually 

 enlarging to aperture, which is 

 about 1 mm. in diameter, bud- 

 ding about one third the distance below the aperture. 



Hamilton of New York and Falls of the Ohio. 



Devonic. 



Fig. 1 79. Hederella canadense, a X 

 b X 12. (After Hall and Simpson.) 



XI. Reptaria Rolle. 

 Like Hederella, but zocecial tubes parallel and closely placed. 

 Devonic. 



16. R. stolonifera Rolle. (Fig. 180, a, b.) Devonic. 



Tubes of equal length, slightly annulated, with the last cell 

 terminal. 



Hamilton of Western New York. 



XII. Mitoclema Ulrich. 

 Minute, cylindrical, branching stems with zocecia bending 

 abruptly outwards and often projecting free. Ordovicic. 



