HEAD-MUSOLES IN GALLUS AND OTHER SAUROPSIDA. 537 



pterygoid arising" from the pterygoid process of the quadrate ; 

 subsequently, the upper end of the external pterygoid muscle 

 extends upwards outside the pterygoid process, and gains 

 attachments to the epipterygoid and side of the skull (text- 

 figs. 28 and 29, pp. 531, 532). 



In Chamgeleon and Tropidonotus the pterygoid Anlage 

 remains single, it loses its attachment to the pterygoid pro- 



ont my/o. 



gen h'yoid / itarnohy ^braorar 



post mylo / br eor ar 



Text-fig. 34. — Sagittal section through an embryo of Chamte- 

 leon. (For explanation of lettering see p. 555.) 



cess and takes origin from the palato-pterygoid bar (text- 

 figs. 33 and 37, pp. 536 and 543). 



In Alligator the pterygoid Anlage also remains single, it 

 grows up outside the pterygoid process to the side of the skull 

 (text-figs. 21 and 22, p. 527). 



It may be concluded that the fixation of the palato-quadrate 

 in the Orocodilia was intimately associated with the upgrowth 

 of the pterygoid muscle, and in the Rhyncocephalia and 



