HEAD-MUSCLES IN GALLUS AND OTHER SAUROPSIDA. 529 



develops into the orbito-quadratns — an elevator of the ptery- 

 goid process of the quadrate (text-fig. 16, p. 523) — though in 

 later periods of development the insertion shifts in part to the 



25. 



Mc. ,' float my/o. ••^ ^rerti 



gnt.my/o. sternohy. 



parach. 



ant my/'o ' post my/o 



yen hyoid sternohy 



Text-figs. 25 and 26. — Sagittal sections through an embryo of 

 Sphenodon, in "stage P-Q" of Howes andSwinnerton.^ 25 is the 

 more external. (For explanation of lettering see p. 555.) 



body of the quadrate, and in part to the hind end of the 

 pterygoid bone. 



In Reptiles the upper part of the myotome (after separa- 



