ii 



H 



ii / . 



y ! 



V I 







30 



THE GEOLOGICAL HISTORY OF PLANTS. 



markings referred to ochorda, Palceophycus, and 



ScoUthus have their , here. Many examples highly 



illustrative of the m j of formation of the impressions 

 are afforded by Canaaian rocks (Fig. 8). 



Branching forois referred to Licrophycus of Billings, 

 and some of those referred to Butliotrephis, Hall, as well 



as radiating markings 

 referable to Scotolithus^ 

 Oyropliyllites, and As- 

 terophycus, are ex- 

 plained by the branch- 

 ing burrows of worms 

 illustrated by Nathorst 

 and the author. As- 

 tropoUthon, a singular 

 radiating marking of 

 the Canadian Cambri- 

 an,* seems to be some- 

 thing organic, but of 

 what nature is uncer- 

 tain (Fig. 9). 



Rhahdichnites and 

 EopTiyton belong to im- 

 pressions explicable by 

 the trails of drifting 

 sea-weeds, the tail-markings of Crustacea, and the ruts 

 ploughed by bivalve mollusks, and occurring in the Silu- 

 rian, Erian, and Carboniferous rocks, f Among these are 

 the singular bilobate forms described as Rusophycus by 

 Hall, and which are probably burrows or resting-places 

 of crustaceans. The tracks of such animals, when walk- 

 ing, are the jointed impressions known as Arthrophycus 

 and CruBiana. I have shown by the mode of occurrence 



* Supplement to " Acadian Geology." 

 t " Canadian Naturalist," 1864. 



f lo. 8. — Palmophycua Beverlyenns (Bill- 

 ings), a supposed Cambrian Fucoid, 

 but probably an animal trail. 



