NIAGARA FALLS AND VICINITY 



131 



These organisms occur as mere impressions on the rock surfaces, 

 varying in slenderness of branches from less than i mm to 5 mm 

 (varieties intermedia and c r a s s a). 







^ ( 



,1 •^ / 



Fig. 25 Bythotrephis gracilis; showing varieties, a B. gracilis; & B. gracilis var. intermedia; 

 c B. gracilis var. crassa 



Found in the shaly partings separating the thin beds of the lower 

 Clinton limestone at Niagara. 



Bythotrephis lesquereuxi 

 Grote & Pitt (Fig. 2.6) 

 (1876. Buifalo soc. nat. 

 sci. Bid. 3:88, 4:20, fig. 6) 



Distinguishing characters. 

 Flattened, erect stem; sim- 

 ple, sparingly dichotomous 

 branches, 3-4 mm thick, 

 gradually widening to near- 

 ly I cm at the very obtuse 



or round truncate point; Fig. 26 Bythotrephis lesauereuxl 



