[Annals N. Y. Acad. Sci., Vol. XXVI, pp. 317-383, PI. IV>-tiJuly, 1915] 



PEESENT STATUS OF THE PEOBLEM OF THE OEIGIN OF 



THE TETEAPODA, WITH SPECIAL EEFEEENCE TO 



THE SKULL AIS^D PAIEED LIMBS ^ 



By ^yILLIAM K. Gregory 



(Presenied before the Academy, 13 Februanj, 1911, IS November, 1911, 

 11 December, 1911, and 10 February, 1913) 



CONTENTS 



. rage 



Comparative study of the skulls of primitive fishes and Stegocephali 317 



Introduction 317 



Ostracodermi, Antiarchi and Arthrodira 318 



Elasmobranchii 320 



Actinopterygii 321 



Dipnoi 322 



Crossopterygii 325 



Stegocephali 334 



Comparative study of the pectoral limbs of primitive fishes and Tetrapoda. 338 

 Origin and early history of the locomotive apparatus of vertebrates. . 338 



Ostracodermi 341 



Arthrodira 342 



Elasmobranchii 343 



Actinopterygii 345 



Dipnoi 348 



Crossopterygii 353 



Stegocepliali 3G5 



"Procoracoid and coracoid" or "coracoid and metacoracoid" ? 369 



Conclusion 375 



Bibliography 376 



J 



CO.MPARATIVE StUDY OF THE SkULLS OF PRIMITIVE FiSHES AND 



Stegocephali 



introduction 



The researches of Credner. Theveniu, Fritsch, Moodie and many others 

 on the amphibians of the Coal Measures, which are the oldest known 

 Tetrapoda, have served on the whole to bring into clearer focns the wide 

 structural hiatus that is still left between the known i^mphibia and the 

 known fishes. For the former without exception have the paired limbs, 

 Avhen present, in the form of cheiropterygia : while in the latter the 



1 Manuscript received by the Editor, March. 1015. (317) 



