OSTEOLOGY OF BIRDS 201 



Next we pass to an investigation of the osteology of the ptar- 

 migans, and in our alpine species, the White-tailed ptarmigan 

 (Lagopus leucurus), we meet with another skeleton, which 

 is again seen to be typically galline, and quite as much so as is the 

 skeleton in G . b a n k i v a itself, or in any of the grouse we have 

 thus far studied in this treatise. Aside from the question of size, 

 the characters it presents as distinguishing it from the skeleton of 

 a specimen of Canachites canadensis, for instance, are 

 of the most insignificant nature. Its skull is seen to be quite after the 

 order of that part of the skeleton in Canachites canaden- 

 sis, as' are also its sternum, pelvis, and limb bones. Indeed I am 

 inclined to think that those two genera are more or less akin to each 

 other, certainly so in so far as their skeletons seem to indicate. The 

 pelvis offers us excellent, I was about to say the best, characters to 

 go by in the skeleton to assist us in determining the affinities of our 

 Perdicinae and Tetraoninae. Its teachings are often evident at a 

 glance, and closer study of the remaining parts of the skeletons of 

 the species being compared, generally support them. Thus far it has 

 in no instance failed me, when I have first referred to it for assist- 

 ance in the manner just mentioned. Marked breadth of pelvis 

 is always associated in the Gallinae with a sternum having com- 

 paratively the broader body, and other skeletal characters are usually 

 associated with these two. G . b a n k i v a has, comparatively 

 speaking, a rather long, narrow pelvis, and we find the body of its 

 sternum very narrow ; so with Coturnix among the Perdicinae, and 

 others. On the other hand Lagopus leucurus possesses an 

 unusually broad and somewhat short pelvis, and its sternal body is 

 anything but narrow for a tetraonine form. 



Osteologically the species of the genus Tympanuchus, as for ex- 

 ample americanus or pallid icinctus (skeletons of both 

 of which I have examined), exhibit several notable departures from 

 the more typical g-alline skeleton. 



The sternum of Tympanuc h us americanus is espe- 

 cially distinguished for the rounded extremities of the external pair 

 of xiphoidal prolongations. 



Still more remarkable is the pelvis of this Prairie hen, which is 

 very broad, very large, and inclined to be massive. Anteriorly its 

 broad ilia are rounded, and they meet very firmly over the sacral 

 crista mesially. Viewed from above, we are to note that the ilia 

 are very distinctly separated from the outer margin, on either side 



