FIRST FORMS OF LIFE. 



29 



modern seas. At the base of the Silurians in western Eng- 

 land, and in what appears the corresponding situation in 

 America, the fossil that perseveres farthest downwards is the 



FIG. 2. 



Lingula anatina. 



I'mgula, a simple bivalve shell. In the same formation, as 

 developed in the chain of mountains crossing the southern 

 part of Scotland, graptolites -p TG 3 



are the lowest fossils as yet 

 found, and next above them 

 appear impressions of an- 

 nelidans, or sea-worms. In 

 a building stone at Lam- 

 peter, in Wales, far down 

 in the Lower Silurians, we 

 find a creature of this kind, 

 supposed to be allied to the 

 nereis of our seas, laid in a 

 long coil, as it might be sup- 

 posed to have arranged it- 

 self when it lay down on the 

 bottom of the sea to die. 

 Another of the characteristic 

 fossils of the very early 

 rocks is orthis, a brachiopod 

 mollusk. Nereltes Cambriensis. 



