300 



CAPT. D. M. S. WATSON ON SEYMOURIA, 



In the Cotylosaurs this division corresponds with that which 

 I have previously founded on the character of the otic notch, 

 and the mode in which a vertically placed quadrate is arrived at. 

 I have recently found that this division on the character of the 

 otic notch applies to all reptiles, affording a sharp distinction 

 between the Anomodonts and all other groups, so that we have 

 now two quite independent series of characters, the otic notch 

 and the structure of the fenestra ovalis, which allow us to split all 

 reptiles, Seymouria excepted, into two groups. Seymouria itself 

 shows characters definitely connecting it with one of these. 



The curious way in which the structure of Seymouria is built 

 up of perfectly well- developed amphibian characters and equally 

 decisive reptilian features, those of intermediate type being very 

 rare, affords a magnificent example of the way in which the 

 evolution of great groups may have taken place by the rapid 

 change of all the definite morphological entities of which it 

 may be regarded as made up, the changes occurring quite inde- 

 pendently and over a considerable time, the passage from the 

 structure of the more primitive to the advanced group being quite 

 gradual when viewed as a whole, but when further considered 

 and analysed found to depend on a rapid evolution of separate 

 regions apparently independently of each other. 



I hope that this study of Seymouria will be regarded as placing 

 beyond dispute the origin of the reptiles from the Embolomerous 

 Labyrinth od on ts. 



I wish to express my thanks to the Percy Sladen Trustees, who 

 paid the expenses of my visit to Texas, to Prof. S. W. Williston, 

 who allowed me to study freely the superb collection of Lower 

 Permian Tetrapods which he has built up in Chicago, to President 

 Osborn and the Staff of the American Museum for similar 

 privileges there, and to Prof. F. Broili, who placed the treasures 

 at Munich at my disposal. I regret that circumstances at 

 present forbid my obtaining his permission to publish a descrip- 

 tion of the Seymouria material of which he gave so excellent a 

 description. Finally, I wish to thank my wife for editing this 

 paper and thereby removing many obscurities. 



Literature. 



Broili, F. 1904. " Permische Stegocephalen und Reptilien aus 



Texas." Pala3ontographica, Bd. li. pp. 1-120. 

 . 1908. " Ein montiertes Skelet von Labidosaurus hamatus 



Cope, einen Cotylosaurier aus clem Perm von Texas." 



Zeitsch. deutsch. geol. Gesell. Bd. lx. Heft 1, pp. 63-67. 

 Broom, R. 1913. " Studies on the Permian Temnospondylous 



Stegocephalians of North America." Bull. Amer. Mus. 



Nat. Hist. vol. xxxii. pp. 563-595. 

 Case, E. C. 1911. A Revision of the Cotylosauria of North 



America. 



