LAUEENTIAN AND EARLY PALAEOZOIC. 



37 



fronds smooth and slightly striate longitudinally, with 

 curved and interrupted striae. Stem thick, bifurcating, 

 the di-visions terminating in irregularly pinnate fronds, 

 apparently truncate at the extremities. The quan- 

 tity of carbona- 

 ceous matter pres- 

 entwonldindicate 

 thick, though per- 

 haps flattened, 

 stems and dense 

 fleshy fronds. 



The species 

 Bufhotrephis sub- 

 nodosa and B. 

 flexuosa, from 

 the Utica shale, 

 are also certain- 

 ly plants, though 

 it, is possible, if 

 their structures 

 and fruit were 

 known, some of 

 these might be 

 referred to differ- 

 ent genera. All 

 of these plants 

 hare either car- 

 bonaceous matter 

 or pxoduce organ- 

 ic stains on the 

 matrix. 



, , The organism 

 with diverging 



wedge-shaped fronds, described by Hall as Sphenothallus 



angustif alius, is also a plant. Fine specimens, in the 



■ collection of the Geological Survey of Canada, show dis- 



Fio. 13. — BiMotrephis Grcmtii, a genuine Alga 

 from the Silurian, Canada. 



