92 



THE CHAIN OF LIFE. 



(Fig. 83). Their discoverer has named them Buthotrephis Hark- 

 nessii and B. radiata^ stating, liowever, that these two species 

 are not improbably portions of the same plant, and that its 

 form is rather that of a land plant than of an Alga. The 

 specimens of these plants which I have seen appear to me to 

 support the conclusion that they represent one species, and 

 this allied to the Aniiularicp. of the Devonian and Carboniferous 

 periods, which probably grew in shallow water with only their 

 upper parts in the air, and bore whorls or verticels of narrow 



rr 



Fig. 84.— American Lower Silurian Plants. — After Lefquereux. 

 a, Sphenophyllum printcBvum. b, Protostigtna sis^illarioides. 



leaves. They were distant relatives of the Mare's-tails, or 

 Equisetums, of cur modern swamps and ponds. 



Somewhat higher up in the Lower Silurian, in the Cincin- 

 nati group of America, Lesquereux finds objects which he 



^ The genus Bnthot>eph''s includes f:upposed branching sea-weeds of the 

 Silurian. For this reason I would propose the name Frotannularia for 

 these plants. 



