XX CONTENTS. 



PAGE 



Echinoderms : The Mastoids, 400. The rise of the cri- 

 noids, 400. The cystoids, 401. Other echinoderms, 401. The 

 continued importance of the brachiopods, 401. The decline 

 of the bryozoans, 405. The continued dominance of the 

 cephalopods, 405. The slow advance of the gastropods and 

 pelecypods, 406. Coral development and the inauguration 

 of reef-building, 407. The initial decline of the trilobites, 408. 

 Other crustaceans, 408. Other marine invertebrates, 408. 

 The scant record of the vertebrates, 408. Marine plants, 409. 

 Foreign Faunas and Migratory Relations 409 



The migratory route, 410. 

 The Closing Restrictional Stage 411 



The advent of a remarkable crustacean fauna, 412. The 

 appearance of scorpions, 415. The presence of fishes, 417. 



CHAPTER VIII. 



THE DEVONIAN PERIOD. 



Formations and Physical History 418 



The Lower Devonian 420 



The Helderbergian series, 420. The Oriskany, 421. 



The Middle Devonian 422 



Local eastern formations, 422. The Onondaga, 422. 

 The Hamilton or Erian series, 426. Middle Devonian in the 

 northwest, 429. The northeastern region, 430. Geographic 

 changes during the Middle Devonian, 430. 



The Upper Devonian 430 



The Tully, Genesee, and Portage formations or Senecan 

 series, 432. The Chemung and Catskill or Chautauquan 

 series, 433. 



Devonian of the West 435 



Areas Where the Devonian Comes to the Surface 438 



Igneous rocks, 439. 



Close of the Devonian 439 



Economic Products 440 



Gas and oil, 440. 



The Foreign Devonian 441 



The continent of Europe, 441. The British Isles, 443. 

 West-central Europe, 447. Russia, 447. Comparison with 

 America, 447. Other continents, 448. 



