GENERAL SUCCESSION OF PLANTS IN TIME. 



43: 



of the Cambrian rocks are concerned, there is every probability that 

 we have to deal entirely with the tracks and trails of marine animals, 

 or with impressions of a purely inorganic character. Thus, the 

 Cambrian fossils referred to such genera as Cruziana and Bilobites 

 are most probably the tracks of Annelides, or the filled-up burrows 

 of Crustaceans. The fossils from the Cambrian rocks of Sweden 

 described under the name of Eophyton, and at one time supposed 

 to be the remains of land-plants, are almost certainly not of a vege- 

 table nature. As previously pointed out (p. 209), strong evidence 

 has been brought forward by Nathorst in favour of the view that the 

 striated markings of Eophyton are really produced by the trailing of 

 the tentacles of Jelly-fishes over the surface of soft sediment. Lastly, 

 the so-called Oldha?)iia of the Cambrian rocks (p. 205) has been 

 regarded as an Alga, but it may have been produced by animal 

 agency, or it may be wholly inorganic. 



From strata of Ordovician age many supposed plants have been 



Fig. 1355. — Licrophycus Otlarvaensis, a supposed " Fucoid " from the Trenton Limestone 

 (Ordovician) of Canada. (After Billings.) 



described, and the great majority of these have been referred to the 

 Alga;, and have been regarded as the remains of Sea-weeds. Most 



