CONTENTS. xxi 



PAGE 



Devonian Life 448 



I. The Marine Faunas 448 



General faunal evolutions, 448. Special faunas evolved, 

 449. The originating tracts of the invading faunas, 450. 



1. The Helderberg Fauna 454 



The marked development of the mollusks, 454. 

 The superior numbers of the molluscoids, 454. The 

 aberrant tendency of the trilobites, 456. The scanti- 

 ness of the crinoids and corals, 456. Minor forms, 457. 

 The notable absence of fishes, 457. 



2. The Oriskany Fauna. • • • 457 



Preponderance of large brachiopods, 458. Mol- 

 lusks abundant and large, 459. Scantiness of trilobites, 

 corals, crinoids, and fish, 459. 



3. The Onondaga Fauna 460 



The presence of true marine fish, 460. The pro- 



. fusion of corals, 463. The unequal development of 



the crinoids, 464. The changes in the brachiopods, 



464. The notable development of the cephalopods, 



465. The persistence of the previous types of the gas- 

 tropods and pelecypods, 466. The revival of the 

 trilobites, 467. Other forms, 467. 



4. The Southern Hamilton Fauna 468 



The progress of the sharks and arthrodirans, 469. 

 The decline of the corals, 470. The advance of the 

 crinoids, 470. The climacteric deployment of the 

 brachiopods, 470. The advance of the cephalopods, 

 473. The abundance of the pelecypods, 473. The sub- 

 ordinate place of the gastropods, 473. Other features, 

 473. 



5. The Northwestern Hamilton Fauna 474 



Brachiopods as evidence of geographic connec- 

 tions, 475. 



6. The Later Devonian (Chemung) Fauna 477 



The Influence of Faunal and Physical Conditions. . . 477 



The Pelagic and Abysmal Life of the Devonian. . . . 479 



Marine Vegetation 479 



The Devonian Fauna in the Great Basin Area 479 



II. The Life of the Land Waters 480 



Principle of interpretation, 480. The remarkable deploy- 

 ment of the crustacean-ostracoderm-vertebrate group, 482. 



