CONTENTS 



PHYLUM VERTEBRATA 



PAGE 



Subphylum VERTEBRATA CRANIATA . i 



Cephalisation, 2; Skull, 11; Brain, 13; Visceral arches, 18; 



Mouth, 18 

 organs, 23 

 system, 26 



Lateral line, 19 ; Nerve components, 21 ; Sense- 

 Pineal eyes, 24 ; Alimentary canal, 26 ; Vascular 

 Kidneys, 27 ; Gonads, 28. 



DIAGRAM OF PHYLOGENY, 29. 



Branch I. and Class CYCLOSTOMATA . . 30 



Skeleton, teeth, 30 ; Somites and nerves, 37 ; Branchial basket, 

 38 ; Nostril, 39 ; Brain, 41 ; Gills, 41; Viscera, 43; Vascular 

 system, 43 ; Kidneys, 43 ; Gonads, 46. 



Sub-Class 1. MYXINOIDEA . 46 



Fam. Myxinidae, 51. 



Sub-Class 2. PETROlVfYZONTIA . 51 



Fam. Petromyzontidae, 54. 



Affinities, 54. 



INCERTAE SEDIS. Fam. Palaeospondylidae, 56. 



Branch II. GNATHOSTOMATA . 58 



Cartilage and bone, 58 ; Skull, 67 ; Vertebral column, 68 ; 

 Median fins, 69 ; Concentration, etc., 71 ; Paired fins, 73 ; Muscle 

 and nerve, 77 ; Nasal sacs, 82 ; Viscera, 82 ; Sense-organs, 82 ; 

 Urinogenitals, 83 ; Chief characters, 92. 



Grade I. Class PISCES 93 



Gills, 63 ; Jaws, 95 ; Vertebral column, 97 ; Axial and 

 appendicular skeleton, 101 ; Caudal fin, 101 ; Skeleton of paired 

 fins, 106; Dermal rays, 109; Vascular system, 109;. Yolk-sac 

 circulation, 114; Alimentary canal, 114; Classification, 117. 

 vii 



