CONTENTS 



PAGE 



Preface ^'" 



The Beginnings of the Fish Skull 75 



Differentiation of the Neurocranium and the Branchiocranium 7' 



Serial Homology of the Jaws with the Gill Arches 79 



The Hyomandibular Problem 80 



Origin of the Orobranchial Apparatus of Gnathostomes 82 



Origin of the Opercular Series 84 



Summary: Four Chief Stages in the Origin of the Jaws, Branchial Arches and Opercular 



Elements 84 



Synopsis of Ten Stages Leading to the Typical Percomorph Skull 85 



Classification and Nomenclature of Skull Parts 88 



Elements of the Preorbital Region ^^ 



Remarks on Dr. Leighton Kesteven's Nomenclature 95 



Are the Premaxillae Compound Elements? 



The Evolution of Particular Skull Types 



99 

 Lower Chordates 



Sharks, Rays, Chimseroids 



TN- • 104 



D'P"°> • •.. 105 



Crossopterygu ^^^ 



Polypterini 



Palseoniscoidei _ 



Chondrostei (Spoonbills, Sturgeons) 



Protospondyli (Semionotids, Pycnodonts, Garpikes, Macrosemiids) 123 



Amioidei 



135 

 IsosPONDYLi (Primitive Teleosts) 



Clupeoidea (Albulids, Tarpon, Herrings, etc.) 



Salmonoidea (Salmon, Smelt, etc.) 



Stomiatoidea ^,. 



Osteoglossoidea ,_ 



Mormyroidea .-r 



Gonorhynchoidea 



.... 181 

 Ostariophysi -„. 



Characins, Gymnotids, Carps and Catfishes 



Heterognathi (Characins) , 



Glanencheli (Gymnotids) 



Eventognathi (Carps, Suckers, etc.) 



Nematognathi (Catfishes) 



.... 200 



Heteromi 200 



Halosaurs (Notocanths) 



202 



Apodes 202 



Eels, Morays 



iii 



