The Zoologist — March, 1871. 



2505 



on either side of the upper mandible. This apparent tuberosity is 

 in reality part of a hinge-like yo/wf, having in itself but slight play, 

 still an undoubted joint. Beyond this joint the upper mandible 

 terminates, as in other swans, geese and ducks, in the nail ; but 

 projecting backwards and slightly outwards from the lower facet of 

 the joint on either side are two rami or long bony processes, 

 thus — 



1. The hinge -like joint. 



2. The bony processes or rami. 



3. The tendon or cheek-string to the backward passage of the processes. 



4. The lower mandible. 



5. The ascending ramus of lower mandible. 



6. The little hook-like process of bone, attached to the processes on either side, 



and provided with muscles to limit and regulate the action of this wonderful 

 mechanism. 



These rami, or processes projecting backwards and outwards, 

 glide upon and over the superior or alveolar border of the lower 

 mandible, checked in their backward progress by a sort of cap- 

 sular ligament in front of, and just external to, the ascending 

 ramus of the lower mandible itself; also in front by a band of 

 tendon attached as a check-string (see No. .3) above to the skull 

 itself and below to the bony process; also, thirdly, by a sickle- 

 shaped bony process projecting inwards, which, whilst it serves to 

 check and regulate the action of the ramus, and through it of the 

 whole upper mandible, has doubtless other offices which it would 

 be most interesting to investigate more thoroughly. These pro- 

 cesses appear to be kept in situ, and to have their movements 



