SKELETON OF THE WILD DUCK. THE SKULL. 319 



with its fellow in the middle line, and forms the posterior 

 boundary of the anterior palatine foramen. The term 

 desmognathous describes the condition of the skull in 

 which the maxillo-palatines fuse with one another in the 

 middle line in this way. 



The quadrate (fig. 60, 12), which unites the two arcades 

 behind, is a stout irregular four-cornered bone forming the 

 suspensorium. It articulates by its dorso-posterior corner 

 with the squamosal, and by its antero-internal corner with the 

 pterygoid. The middle of its ventral surface forms a hemi- 

 spherical knob with which the mandible articulates, while its 

 dorso-anterior border is drawn out into a long point which 

 extends towards the interorbital septum. 



(3) THE MANDIBLE. 



The mandible or lower jaw consists of two rami which 

 are flattened and fused together in the middle line in front, 

 while behind they diverge from one another and articulate 

 with the quadrates. 



Each ramus is composed of five bones fused together, one 

 being a cartilage bone, and the other four membrane bones. 

 The articular is the only cartilage bone of the mandible, 

 it bears the double condyle (figs. 59 and 60, 13) or concave 

 articular surface for the quadrate, and is drawn out behind 

 into a large hooked posterior articular process. The ar- 

 ticular is also drawn out into a prominent process on each 

 side of the articular surface for the quadrate, and is marked 

 by a deep pit opening posteriorly. The articular is continuous 

 in front with Meckel's cartilage which forms the original 

 cartilaginous bar of the lower jaw, and is ensheathed by the 

 membrane bones. Of these the supra-angular forms the upper 

 part of the mandible in front of the articular, its dorsal sur- 

 face is drawn out into a small coronoid process, its outer 

 surface also bearing a prominent process. The angular is 



