CROSSBILL. 205 



woodcuts (figs. 1, 4, b), for this covers the other two. They 

 all have their origin on the occipital bone and are attached 

 to the mandibula behind the centre of motion, so as, by 

 their simultaneous contraction, to lower its anterior part. 

 The lower portions of the quadrates are, by this compres- 

 sion, pushed somewhat forwards, assisted by two smaller 

 muscles not represented, but the position of which may be 

 understood (fig. 3). One of them, which is small and flat, 

 arises from the interorbital septum, behind the optic foramen, 

 and passing downward is attached to the styloid process of 

 the quadrate. The other is pyramidally shaped, arising 

 also from the septum, but in front of the former, and passing 

 downward and backward is attached to the pterygoid. Both 

 these muscles in contracting pull the quadrate forward and 

 thus raise the maxilla. The depressors of the lower jaw 

 and elevators of the upper therefore act together to open the 

 bill. To close it the temporal and pterygoid muscles raise 

 the mandibula, while two slender slips (fig. 2, d, d) which 

 extend forwards to t\e premaxillaries combine to bring them 

 down. When latj^l motion is required the great pyramidal 

 on the right pulls the end of the mandibula, to which it is 

 attached, backwards, the pterygoid muscle on the left at the 

 same time assisting by carrying that side of the mandibula 

 inwards. 



Having thus described these muscles, their peculiar action 

 in the Crossbill must be related. The bird partly opening 

 its mouth brings the points of the bill from their ordinary 

 crossed position to be directly over each other. In this 

 reduced compass they are inserted between the scales of the 

 cone on which it is about to feed and then in the act of sepa- 

 rating them still more widely the mandibula is drawn side- 

 ways and thus forces the scales asunder. 



At this stage the tongue is brought into play. The 

 anterior end of the hyoid has attached to it a narrow bony 

 projection covered with horn (figs. 6, 7, a), about three 

 eighths of an inch long, extending forwards and downwards, 

 its sides curved upwards, and shaped at the tip like a scoop, 

 while at the proximal end there are two small elongated pro- 



