308 New York State Museum 



the close of the Silurian. Among the mountain ranges 

 formed were the Caledonian ranges of Great Britain 

 which extended across Ireland and Scotland to northern 

 Spitzbergen. 



In addition to the fossil iron ores of the Clinton and 

 the gypsum and salt of the Salina beds the Silurian 

 (upper) is rich in dark-blue, impure, magnesium lime- 

 stones of shallow-water origin, the waterlimes which 

 are the natural cement rocks that were formerly so 

 extensively quarried for the making of portland cement. 



Life. During the Silurian four faunal provinces were 

 represented in the continental seas : the Arctic, the 

 Atlantic, the Southern (Gulf of Mexico) and the Cor- 

 dilleran which is not well known but is believed to be 

 Pacific. An important center of origin was the Arctic, 

 which during Lower and Middle Silurian extended al- 

 most as far south as the Ohio river and included a 

 large part of the northern interior area of the conti- 

 nent. The Arctic waters were warm and corals grew 

 abundantly in the Arctic region as well as in Canada 

 and the Michigan-Wisconsin area. The fauna shows 

 a connection with the Baltic area of northern Europe 

 and indicates a connection with this region by way of 

 the St Lawrence trough and Greenland. The fauna of 

 the Atlantic province entered the interior by way of 

 the northern end of the Appalachian trough, then in 

 communication with the North Atlantic. Many of the 

 species of this province also occur in the rocks of west- 

 ern Europe, especially England, since that area, too, 

 communicated with the North Atlantic. The fauna of 

 this province is most abundantly found in the rocks of 

 Anticosti Island in the Gulf of St Lawrence. 



