OSTEOLOGY OF BIRDS 33 1 



O . buccinator. It is very likely that all three of these forms 

 agree closely in so far as their osteology is concerned, so that what 

 is said here in reference to the skeleton ofO. columbianus 

 will apply with equal truth to any one of them. In any event, the 

 majority of the characters of the bones agree with those found 

 among the Anseres generally, and the skull of a swan is essentially 

 constructed upon identically the same pattern as that part of the 

 skeleton in any of the ducks or the geese. 



SKELETON OF OLOR COLUMBIANUS 



(See plates i, 2) 



Skull. This swan has a skull that has an average length of 

 16.3 centimeters, measuring from the summit of the supraoccipital 

 prominence, to the most distal point upon the apex of the rounded 

 superior mandible. 



Upon comparing the characters of it with the corresponding ones 

 of many other anserine birds before me, I find that it comes nearest 

 in these particulars to the skull of Branta canadensis. This 

 refers not only to the cranium, but to the mandible and the skeletal 

 parts of the hyoidean apparatus, as well. Indeed, apart from the 

 difference in size, the characters of the skull and hyoid of Branta 

 canadensis are practically repeated in those parts in the skele- 

 ton of Olor columbianus. To describe the essential char- 

 acters of the one, is to describe those of the other. In Olor the 

 osseous auricular opening is relatively smaller than it is in the 

 goose, and the passage for the rhinal nerves above the interorbital 

 septum in either orbit, may be largely arched over with bone in 

 the former ; and a forward projecting spicula of bone, held in place 

 in front by the maxillopalatines indicates in the swan a rudimentary 

 internasal septum, that is absent in Branta. All these points 

 however, are trivial, and in no way detract from the statement, 

 that, with respect to characters, these skulls are to all intents 

 and purposes, identically alike. 



The angular processes at the posterior free ramal ends of the 

 mandible, are in Branta relatively longer, more pointed, narrower 

 vertically, and less curved than they are in Olor colum- 

 bianus. Otherwise, as has already been said, the jaws of these 

 fowls agree in their essential characters. 



Remainder of the trunk skeleton. As is shown in a table 

 [p. 285] this swan has at least eight more vertebrae in its 

 spinal column than are possessed by any of the ducks; and 



