AGE OF COAL. 



233 



Fig. 135. 



there were also many spe- 

 cies. One of them is repre- 

 sented in Fig. 136, show- 

 ing the spiral support from 

 which it takes its name, a, 

 as it is in the shell, and #, 

 apart of it taken out. The 

 - strange Orthoceratites, 

 which, like the Crustacean 

 Trilobites, were abundant 

 in the Silurian age, now, 

 like them, appeared with 

 but few species, and, be- 

 fore the age had passed, 

 became extinct. 



Fig. 13C. 



335. Permian Period. The Carboniferous age ended 

 with what is called the Permian period, in which no coal 

 was formed. This period has its name from a portion 

 of Russia which was in ancient times the kingdom of 

 Permia. Here the rocks of that period cover an area 

 700 miles long and 400 broad. Until quite recently, it 

 was supposed that there are no Permian strata in this 

 country ; but they have been discovered in Illinois, Kan- 

 sas, and some parts of the slope of the Rocky Mountains. 

 In this period nearly all the country east of the Mississip- 

 pi was dry land, and therefore all the Permian deposits 

 were made on the west of it, with the exception of a small 

 part of Illinois. In Europe there are Permian strata in 

 Central Germany, and in England in the neighborhood 

 of the coal regions, in addition to the extensive area cov- 



