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CONTENTS 
Side-Gilled Saw-Fislaes (Pristiophorus) — True Saw-Fishes (Pristis)— Beaked Rays 
(Rhinobatidce )—Typical Genus ( Rhinobatis)—Rhynchobatis —The True Rays, or Skates 
( Raiidce) —Electric Rays (Torpedinidce)— The Eagle-Rays (Myliobatidai)— Typical Genus 
(Myliobatis)— Other Genera ( Aetobatis , etc.)—Sting-Rays (Trycjonidce)— Lobe-Finned 
Sharks (Ichthyotomi) — Fold - Finned Sharks (Cladodontia) — Spine - Finned Sharks 
(Acanthodii), ..... • 
THE LOWEST VERTEBRATES AND THEIR 
ALLIES 
CHAPTER I.— The Lamprey Group, —Class Cyclostomata. 
Characters of Chordates and Non-Chordates— Lampreys and Hag-Fishes (Subclass 
Marsipobranchii )—True Lampreys ( Petromyzum) —Southern Lampreys ( Mordacia , etc.) 
—Hag-Fishes ( Myxinidce) —Primeval Lampreys ( Palceospondylus ), 
CHAPTER II.— The Armoured Primeval Vertebrates, —Subclass Ostracophori. 
Pteraspis — Cephcdaspis — Pterichthys, ........ 
CHAPTER III.— The Lancelets, —Subkingdom Protochordata —Class Leptocardii. 
Common Lancelets ( Branchiostoma ), ........ 
CHAPTER IV.—' The Sea-Squirts or Ascidians,— Class Tunicata. 
Structure of Ascidians—Development—Typical Ascidians—-Non-Luminous Pelagic Ascidians 
—Tailed Ascidians, . . ...... 
CHAPTER V.—Worm-Like Protochordates,— Class Enteropneusta. 
Balanoglossus —Other Forms—Ancestry of Chordates, ...... 
Index ............ 
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