98 HISTORICAL PALEONTOLOGY. 



Of the life of the Lower Silurian period we have record in a 

 vast number of fossils, showing that the seas of this period 

 were abundantly furnished with living denizens. We have, 

 however, in the meanwhile, no knowledge of the land-surfaces 

 of the period. We have therefore no means of speculating 

 as to the nature of the terrestial animals of this ancient age, 

 nor is anything known with certainty of any land-plants which 

 may have existed. The only relics of vegetation upon which 

 a positive opinion can be expressed belong to the obscure 

 group of the " Fucoids, " and are supposed to be the remains 

 of sea-weeds. Some of the fossils usually placed under this 

 head are probably not of a vegetable nature at all, but others 



Fig. 36. LicropJiycua Ottawctensis, a " Fucoid," from the Trenton Limestone 

 (Lower Silurian) of Canada. (After Billings.) 



(fig. 36) appear to be unquestionable plants. The true affin- 

 ities of these, however, are extremely dubious. All that can 

 be said is, that remains which appear to be certainly vegetable, 



