PRE-CARBONIFEROUS FLORAS. 



479 



the Lower Silurian Rocks no undoubted traces of land-plants 

 have hitherto been detected. The deposits of this period, 

 however, have yielded numerous fossils which have been re- 

 ferred to " Fucoids," under the generic titles of Palceophycus, 

 Licrophycus, Buthotrephis, Phytopsis, Sphenothallus, &c. Some 

 of these appear to be nothing more than the tracks of Annel- 

 ides. Others appear to be unquestionable plants ; but nothing 

 positive can be stated as to their affinities. They may be Algce, 

 or they may belong to plants higher in the vegetable scale. 

 Subjoined is an illustration of a characteristic Canadian species 

 described by Mr Billings (fig. 379). 



Fig. 379. Licrophycits Ottawaeiisis, a " Fucoid" from the Trenton Limestone 

 (Lower Silurian) of Canada. After Billings. 



In the Upper Silurian Rocks are also numerous remains ot 

 " Fucoids " (Arthrophycus, Dichwlites, Chondrites, Spirophyton, 

 &c.), which do not differ in any important point from those ot 

 the inferior division. Some of these can hardly be anything 

 but true plants, and would certainly seem to be the remains of 



