204 GEOLOGr. 



which I have spoken in 262. Indeed, there has actu- 

 ally been found some coal in some of the rocks, in addi- 

 tion to the carbonaceous shales, which appear now as 

 they did in the Silurian system. 



296. Animal Life. As there was a considerable ad- 

 vance upon the previous age in the forms of vegetable 

 life, there was a corresponding one in those of animal 

 life. Few, if any, vertebrates existed in the Silurian age, 

 but now they abounded in the form of fishes. Some rep- 

 tiles also appeared, though not in much variety. There 

 is no evidence of the existence of any insects, or birds, 

 or mammals. 



297. Mollusks. Of the Mollusks there was as abun- 

 dant a variety of species as in 



the previous age. Of the Bra- 



Fig. 113. 



chiopods, the genus Stri- 

 gocephalus, of which Fig. 

 113 represents one spe- 

 cies, was introduced at 

 this period. Of the Ce- 

 phalopods, the genus Cly- 

 menia was introduced, of 

 which Fig. 114 represents 

 one species. Thirty- five 



Fig. 114. -.!. T. -. 



species, which is nearly 



all under this genus, have been found in the rocks of one 

 locality in Bavaria. 



298. Crustaceans. The Trilobites, whose species were 

 numbered by the hundreds in the Silurian age, now 

 amounted to a dozen or two. But there are some very 

 extraordinary Crustaceans, which, beginning to appear 

 in the age of Mollusks, were now very abundant. They 



