54 ANNALS NEW YORK ACADEMY OF SCIENCES 



where many of the new discoveries are due to the synthesis of the study 

 of present forms with those of the past, so that a department of palaeon- 

 tology should combine in its collections a complete series of the modern 

 with the fossil forms, if correct interpretations are to be made of the 

 fossil material. 



The factor that has been most neglected has been the study of the 

 myology along with the bony structure of the fossil forms. The bones 

 of the skeleton should be studied not as independent elements, but as 

 supports for the muscles that covered or were attached to them. The 

 skull of an ophidian studied merely as an osteological specimen shows 

 much in the way of specialization and peculiar development, but without 

 the study of the motive power for which it furnishes the support the 

 results are rather barren, as too much has been left out of consideration. 

 It is like making a study of a complex series of levers without taking 

 into consideration the forces that move them. A few papers and books 

 do indeed consider the correlation of the bones and muscles in modern 

 forms, especially man, such as Bardeleben (1903), Fick (1904-1910- 

 1911), Strasser (1908). These studies on modern forms give the key 

 for similar work on the fossils, as the principles of mechanics concerned 

 hold throughout. Prof. W. K. Gregory (1912) has endeavored to correlate 

 palaeontology, osteology and myology in his studies on the evolution of the 

 limbs of recent and fossil ungulates. His discussion of the angle of in- 

 sertion of the muscles upon the limb bones, in relation to power and 

 speed, bears upon the study of jaws and jaw muscles. Realizing the need 

 of further studies of this kind. Dr. Gregory suggested that I should take 

 up the pro])lem of the evolution of the jaw muscles of vertebrates in rela- 

 tion to skull structure. 



In this paper I have accordingly had before me the following aims : 

 first, to follow the jaw muscles through a selected series of vertebrates 

 ranging from shark to man and to express the essential facts in clear and 

 semidiagrammatic drawings of uniform character and treatment, to facili- 

 tate comparison; second, to discover and summarize the homologous re- 

 lations of the several jaw muscles throughout the series and thus attempt 

 to clear up and harmonize the confusing synonymy due to varying systems 

 of nomenclature founded on special types ; third, to discover the adapta- 

 tional relations between skull structure and musculature ; fourth, to apply 

 these principles to a reconstruction of the musculature in certain extinct 

 vertebrates, especially those of great general phylogenetic importance in 

 the different classes. 



