MESOPTERYGOID IN CERTAIN REPTILIAN SKULLS. 



457 



opening, it forms a large support to the basisphenoid cartilage, 

 especially in the neighbourhood of the basipterygoid process. 

 In front this median vomer or " parasphenoid" extends forward 

 as a support to the median septum almost exactly as does the 

 mammalian vomer. 



The fossil Tetrnpod slvuU that has given us the clue to the real 

 affinity of the "meniscus" is that of ^' Seymour ia hai/lorensis'' 

 Broili, recently described by Watson. ■' Seymouria " is one of the 

 most interesting primitive fossil types ever discovered ; and 



Text-fioiu'e 6. 



E.Pt. Pt. M.Pt. 



'^■''^- B.Pt.P. 



Transverse sections through the mesopterygoid and related elements in the skull 

 of the embryo Agama shown in Fig. 5. 

 A. Through the posterior part of the element. 

 15. A section near the middle. 

 C. A section near the anterior end. 



Broili, Williston, and Watson have revealed to us nearly eveiy 

 detail of its structure. There are, however, two points on which 

 one would like to remark. Williston, v. Huene, and Watson all 

 agree that Seymouria haylorensis Broili is the same animal as 

 Gonodectes favosus Cope. Cope's type skull is in the American 

 Museum, and Jiis description, though by no means such as would 

 enable anyone to identify readily a similar species, is fuller than 

 that of many types, and I cannot agree with Watson that Cope's 



