Explanation of Plate VIII 



Jaw muscles of a typical bird : (Julius 



Fig. 1. — Gallus. Superficial muscles. 



The capiti-mandibularis is divided iuto a superficial layer, analogous with 

 the masseter of mammals, and a deep layer, analogous with the temporalis. 

 The capiti-mandibularis superficialis (C.m.s.) is attached to the quadrate. 



Fig. 2. — Galius. 



Deep muscles after removal of the capiti-mandibularis superficialis et medius. 



The pterygoideus anterior (Pt. ant.) has the normal reptilian relations. 

 The pterygoideus posterior (Pt. post.) perhaps is attached to the quadrate. 

 The depressor mandibular (D.m.) is of normal reptilian type. 



Fig 3. — Gallus. 



Deep muscles as seen from below. The entotyinpanicus (En. ty.) muscle is 

 a remnant of the adductor mass of lower vertebrates. The parieto-mandib- 

 ularis (Pa. m.) seems to represent a part of the depressor mandibular of 

 reptiles. 



