OSTEOLOGY OF BIRDS 28l 



are greatly produced directly backward, to be abruptly recurved 

 upward at their extremities. (This is the style also in Olor, but in 

 the Hutchins goose they are saber-shaped and gradually recurve up- 

 ward.) Beyond this process the articular facet projects from the 

 ramal side, and at a varying distance (for the species) ; in front of 

 this we find a constant process for muscular attachment. This last 

 is situated at about the middle of the deepest and most platelike 

 portion of the ramus, and in a swan is ridgelike, being connected 

 with the coronoid process on the edge of the bone immediately 

 above it. 



In front of this the ramal vacuity, here a narrow slit, is usually 

 completely closed by the splenial element. 



The bone now becomes shallower in the vertical direction, its 

 superior and inferior borders rounded, while a well defined gutter 

 for the passage of nerves and vessels marks its entire length. 



As a rule, among the Anatinae the symphysis is rather deep, 

 rounded beneath, and correspondingly concave above, the under 

 side being thickly studded with vascular foramina. Spatula has 

 a somewhat different anterior ending from this [fig. 19]. In 

 the middle line in front a sort of " nail " is developed like the 

 one found on the superior mandible, though not so strong. The 

 superior ramal margins are continued round this projection, form- 

 ing its edge, while the spoonlike dilatation is insured by the outer 

 ramal sides shelving away from this upper border, so as to face up- 

 ward and outward rather than directly outward, as they do 

 posteriorly. 



The form most common for the mandible to have is well ex- 

 emplified in that of Clangula [fig. 20]. 



The articular projections in the mandible of this duck lie nearly 

 in the horizontal plane, and each one supports the two concavities 

 for the mandibular foot of the quadrate. A rather slender in- 

 turned process directed upward and toward the medial plane pro- 

 jects from the inner one. This may present a small pneumatic 

 foramen at its extremity. Beneath either of these articular por- 

 tions of the mandible, and to the inner side of the angular process, 

 we discover a deep conical fossa, with its apex to the front. 



It is intended for muscular insertion, and is present, I believe, 

 throughout the group. 



The mandible is very imperfectly pneumatic, particularly in the 

 Brant, where the bone sometimes, if not always, entirely bcks this 

 condition. 



