12 contp:nts 



CHAPTEE XXII p^^j^ 



Representative Insects (By Vasco M. Tanner) ________ 343 



The Locust, 343; The June Bug, 354; The Honey Bee, 357. 



CHAPTER, XXIII 

 Phylum Chordata _______-____-_--- 360 



Characteristics, 360; Classification, 361; Phylogenetic Advances 

 of Chordata, 362; Protochordata (Lower Chordates), 362; Subphylum 

 Hemichordata, 362; Subphylum Urochorda, Molgula, 365; Subphylum 

 Cephalochorda, Amphioxus, 368. 



CHAPTER XXIV 



The Vertebrate Animal: Subphylum Vertebrata _______ 375 



Classification, 410. 



CHAPTER XXV 



Cyclostomata __________________ 412 



Classification, 412 ; Economic Relations of the Class, 413 ; The Lamprey, 

 413; Habitat, 413; Habits and Behavior, 415; External Structure, 

 415; Internal Structure, 415. 



CHAPTER XXVI 



Elasmobranchii __________________ 422 



Classification, 422; Economic Relations of the Class, 425; The Spiny 

 Dogfish, 426; External Features, 426; Muscular System, 427; Skeletal 

 System, 427; Digestive System, 430; Circulatory System, 431; Respira- 

 tory System, 435; Nervous System, 435; Urinogenital System, 437; 

 The Eonnethead Shark, Reniceps (Sphyrna) Tiburo Compared to 

 Squalus, 439. 



CHAPTER XXVII 



Pisces, True Fish _________________ 442 



Classification, 445; Economic Relations of the Class, 455; Typical 

 Bony Fish — Yellow Bullhead and Some Comparisons With Yellow 

 Perch, 457; External Features, 457; Digestive System and Digestion, 

 458; Circulatory System and Circulation, 459; Respiratory System, 

 463; Excretory Organs, 464; Skeletal System, 464; Muscular System 

 and Locomotion, 467 ; Nervous System, 469 ; Reproduction and the 

 Life History, 470. 



CHAPTER XXVIII 



Class Amphibia (By Ottys Sanders) ___________ 472 



Classification, 482; A List of Families of the Amphibia in the United 

 States, 484; Order Caudata (Urodela) (Tailed Amphibians), 484; 

 Order Salientia (Anura) (Tailless Amphibians), 485; Economic Im- 

 portance, 486; Necturus Maculosus, the Mud Puppy, 487; Food and 

 Digestive System, 489; Circulatory System, 490; Respiratory Sys- 

 tem and Breathing, 491; Urinogenital System, 492; Skeletal System, 



