MORPHOLOGY OF CRAXIAL MUSCLES IN SO.AIE VERTEBRATES. 195 



levator Tnfixilla3 superioris of Selachians disappears in 

 Amphibia.^ Tliere' is, however, no ti-ace of this in the on- 

 togeny of Amphibia. According to Gaupp the pterygoid 

 process of Amphibia presents features which lead to the 



Text-fig. 22. 



oH Ut«vtN 



<^OT\-a.ote>nL 



22. 



^.cipenser, embryo 8k mm. The left side of the section is 

 slightly anterior to the right. 



suggestion that it is in process of " Kiickbildung," If this 

 be so, and if the pterygoid process of Amphibia be homo- 

 logous with that of Selachians — a matter which Gaupp says 



> The levator maxillae superioris "'ist wohl mit der Verwandliing der 

 Streptostylie in die Mouimostylie der Urodela verloren gegangen." 



