UPPER SILURIAN. 



223 



H. Life. 



The rocks of the Medina epoch in New York, and farther west, 

 contain few fossils, while those of the Clinton abound in them. The 

 Anticosti beds of the same era show that there was a profusion of 

 life in the seas, through both epochs. The Niagara beds are generally 

 full of fossils. 



1. Plants. 



The only fossil plants are AlgaB (sea-weeds), called Fucoids. Forms 

 referred to this group are common in the sandstones of the Medina 

 and Clinton beds, but rare in the limestones of the Niagara period 

 (limestones seldom containing fossil sea-weeds). Fig. 398 represents 

 portions of a fossil supposed to be the cast of a sea-weed. It has 

 been suspected to be the cast of the tracks of large worms. It covers 

 thickly some layers of the Medina sandstone. Other fucoids of these 

 rocks are rounded branching stems, from the size of a thread to that of 



a finger. 



2. Animals. 



The sandstones and shales of the Medina and Clinton groups con- 

 tain, besides great numbers of Brachiopods, many Lamellibranchs, 

 with few Corals or Crinoids ; while the limestones of the Clinton 



Figs. 398-403, 



Fig 398, Arthrophycus Harlani ; 399, Lingulella cuneata ; 400, Modiolopsis orthonota; 401, M. (?) 

 primigenia; 402, Pleurotomaria litorea ; 403, Bucanella trilobata. 



group, and especially those of the Niagara, abound in Brachiopods, 

 Corals, Crinoids, and Trilobites, and contain few Lamellibranchs or 

 muddy-bottom species. Some of the limestone beds were originally 

 coral reefs. No evidences of fishes or freshwater life have been 

 observed. One of the most common Medina species is a 



