x CONTENTS 



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Fresh- Water Herrings (Diplomystus) Anchovies (Engraulis) Elops Slender 

 Scales (Leptolepis) The Smooth Heads (Alepocephalidce) Southern Salmon 

 (Haplochitonidce) Salmon Tribe (Salmonidce) Typical Group (Salmo) Salmon 



Trout Charr Many-Rayed Salmon (Onchorhynchus) Smelts (Osmerus) 

 Coregonoids (Coregonus) Grayling (Thytnallus) Percopsida Bony Pike and 

 Its Kindred (Suborder sEtheospondyli) Existing Types (Lepidosteidce) Spear 

 Beaks (Aspidorhynchidte) The Bowfin and Its Allies (Suborder Protospondyli) 

 Existing Family (Amiidce) Extinct Families (P achy cor midcz, etc.) The Sturgeon 

 Tribe (Suborder Chondrostei) Toothed Sturgeons (Polyodontidce) Toothless 

 Sturgeons (Acipenserida) True Sturgeons (Acipenser) Shovel-Beaked Stur- 

 geons (Scaphirhynchus) Allied Extinct Families ( Chondrosteidce, etc.) Fringe- 

 Finned Ganoids (Order Crossopterygii) Existing Species (Polypteridce) Extinct 

 Families, ....... ... 2701 



CHAPTER IV. SHARKS AND RAYS, Subclass Elasmobranchii. 



Distinctive Features The Blue Shark and Its Allies (Carchariidce) Typical Genus (Car- 

 charias) Tope (Galeus) Hammerheads (Sphyrna) Hounds (Mustelus) Por- 

 beagle Group (Lamnidce) Porbeagles (Lamna) Rondeleti's Shark (Carcharodon) 



Fox Shark (Alopecias) Basking Shark (Cctorhinus) Indo-Pacific Basking 

 Shark (Rhinodontidce) Dogfishes and Their Allies (Scylliida;) True Dogfishes 

 (Scyllium) Other Genera Pavement-Toothed Sharks (Cestraciontidcz) Comb- 

 Toothed Sharks (Notidanidce} Typical Genus (Notidanus) Frill-Gilled Shark 

 (Chlamydoselache) The Spiny Dogfishes and Their Allies (Spinacidce) The 

 Extinct Petalodonts (Petalodontidce) The Angel Fish (Squatinidce) The Saw- 

 fishes (Pristiophoridce and Pristidce} Side-Gilled Sawfishes (Pristiopfiorus) 

 True Sawfishes (Pristis) Beaked Rays (Rhinobatidce) Typical Genus (Rhino- 

 batis) Rynchobatis The True Rays or Skates (Raiidce) Electric Rays ( Tor- 

 pedinidce) The Eagle Rays (Myliobatidce) Typical Genus (Myliobatis) Other 

 Genera (Aetobatis, etc) Sting Rays (Trygonidce} Lobe-Finned Sharks (Ichthyo- 

 tomi) Fold-Finned Sharks ( Cladodontia) Spine-Finned Sharks (Acanthodii) , . 2895 



THE LOWEST VERTEBRATES AND THEIR ALLIES 



CHAPTER I. THE LAMPREY GROUP, Class Cyclostomata. 



CHARACTERISTICS OF CHORDATES AND NON-CHORDATES Lampreys and Hagfishes 

 (Subclass Marsipobranchii) True Lampreys (Petromyzum) Southern Lampreys 

 (Mordacia, etc.) Hagfishes (Myxinidce) Primeval Lampreys (Palceospondylus), 2925 



CHAPTER II. THE ARMORED PRIMEVAL VERTEBRATES, Subclass Ostracophori. 

 Pteraspis Cephalaspis Pterichthys, ....... 2932 



CHAPTER III. THE LANCELETS, Subkingdom Protochordata Class Leptocardii. 

 Common Lancelets (B ranch iostoma), ....... 2935 



CHAPTER IV. THE SEA SOJJIRTS OR ASCIDIANS, Class Tunicata. 

 Structure of Ascidians Development Typical Ascidians Non-Luminous Pelagic 



Ascidians Tailed Ascidians, ... ..... ^6 



CHAPTER V. WORM-LIKE PROTOCHORDATES, Class Enteropneusta. 

 Balanoglossus Other Forms Ancestry of Chordates, ..... 2951 



INDEX 2955 



