CONTENTS XV 



PACE 



2. Class I. Crustacea 276 



a, The Crayfish — Cambarus, 276 ; b, Crustacea in 

 General, 292. 



3. Class II. Onychophora 305 



4. Class III. Myriapoda 308 



5. Class IV. Insecta 312 



a, The Honey-bee, 312; b, The Anatomy and Physi- 

 ology of Insects in General, 328; c, General Survey 

 of the Orders of Insects, 336 ; d, The Economic Im- 

 portance of Insects, 370. 



6. Class V. Arachnida . 371 



a, The Spiders, 371 ; b, Other Arachnida, 377. 



CHAPTER XIV 



Phylum Chordata: Introduction. 



1. Subphylum I. ENTEROPNEUSTA 



2. Subphylum II. TUNICATA .... 



3. Subphylum III. CephalOCHORDA . 



4. Subphylum IV. VERTEBRATA : INTRODUCTION 



CHAPTER XV 



386 

 386 



389 

 393 



400 



Subphylum Vertebrata : Class I. Cyclostomata . . . 414 



1. The Lamprey — Petromyzon 4 I 5 



2. Cyclostomata in General 4 2 ° 



CHAPTER XVI 



Subphylum Vertebrata : Class II. Elasmobranchii ] . . 422 



1. The Dogfish -Shark — Squalus acanthias . . . 4 22 



2. Elasmobranchs in General 428 



3. The Economic Importance of Elasmobranchs . . . 43 1 



CHAPTER XVII 



Subphylum Vertebrata: Class III. Pisces .... 43 2 



1. A Bony Fish — The Perch 43 2 



2. An Abridged Classification of Living Fishes . . • 443 



