52 ANNALS NEW YORK ACADEMY OF SCIENCES 



Page 



Mammalia 102 



Monotremes i Ill 



Didelphys 115 



Solenodon 116 



Mus ' 117 



Felis 118 



Homo 119 



Reconstructions of the jaw muscles in certain extinct vertebrates 120 



Placodermi 120 



Dinichthys 123 



Eryops 128 



Labidosaurus 130 



Tyrannosaurus 132 



Cynognathus 134 



Homologies of the jaw muscles in vertebrates 137 



Introduction 137 



Homology in the Pisces 140 



Homology in the Amphibia 144 



Homology in the Reptilia 146 



Homology in the Aves 148 



Homology in the Mammalia 149 



General summary of homologies 153 



Relations of jaw muscles to the temporal fenestra? of reptiles 154 



Tables I-V summarizing the homologies of the jaw-elements in Fishes, 



Amphibia, Reptiles, Birds, Mammals and Vertebrates as a whole . . . 156 



Bibliography - 160 



INTRODUCTION 



This paper attempts first to trace the muscles of mastication from their 

 origin in the primitive gnathostomes to their perfected development in 

 the higher vertebrates and secondly to discover the co-adaptations of 

 musculature and skull structure. 



There has been a great neglect of the correlation between osteology and 

 myology. Hundreds of monographs are at hand on both subjects, yet 

 synthetic studies that deal with both and with their interrelationships are 

 extremely rare. As muscle was no doubt in existence before bone, and as 

 there is the closest relation between the two, we should naturally con- 

 sider myology and osteology together instead of under separate heads. 



Many monographs have been written on the myology of special forms, 

 but usually with little consideration of the conditions to be found in 

 related groups. Apart from the great work by Euge on the seventh nerve, 

 there have been few general surveys attempted. Ruge traced the facialis 

 nerve and its musculature from the elasmobranchs to mammals, giving 



