OSTEOLOGY OF BIRDS 28 1 



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 dififierent anterior ending from this [fig. iq]. 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 lacks this 

 condition. 



