PROCEEDINGS OF THE NATIONAL MUSEUM 



M. protractor 

 quad rati et 

 pterygoidei 



ramus of lower jaw 



M. depressor 

 mandibulae 



articular 

 juc/omandibular lig. 



Hesperfphona vespertine 



ramus of lower jaw postorbital 

 ligament 



M. protractor quadrati 

 et pfery^oidei 



drate 



M. depressor 

 mandibulae 



retroarticular 

 process 



articular 

 jugomandibular lig. 



Gallus domestfcus 



Figure 1. — Structural features of the head in the evening grosbeak (Hesperiphona vespertina) 

 and domestic chicken {Gallus domesticus). (Adductor and retractor muscle groups 

 removed.) 



