284 Shufeldt on a Hybrid Grouse. Ll""v 



ferent from that part of the skeleton in any other kind of North 

 American Grouse. It is approached by the pelvis in Pcdioccztes, 

 but not to such a marked degree as it is by the bone in this 

 hybrid fowl. 1 Viewed laterally, the most obvious character is the 

 remarkable manner in which, upon either side, the post-ace- 

 tabular part of the ilium far over-arches the lateral surface of the 

 pelvis and the ischiac foramen. To a very moderate extent this 

 is apparent in the pelvis of Pedioccetes, whereas in the hybrid 

 we have the condition much more pronounced, but not to the 

 extent that it is in the Prairie Hen. Again, in the latter, upon 

 superior view of the pelvis, we note, in the post-acetabular part, 

 that the sacrum is separated from the inner margins of the ilia 

 by quite an interval. This is not nearly so well marked in the 

 hybrid, while in Pedioccctes those borders are in close contact 

 for their entire lengths. The pubic elements are produced 

 posteriorly, not being as short as they are in Tympanuchus, but 

 more as we find them in the Sharp-tail Grouse. In all its minor 

 characters, as I have said above, this pelvis is an exact inter- 

 mediate between the pelves as they occurred in its parents. 

 Such an observation is quite applicable, too, to the sternum, 

 which appears to be just a shade off from that bone in Tympanu- 

 chus, but differs in one insignificant minor character in that the 

 antero-superior produced portion of either costal process in the 

 hybrid is somewhat lengthened, very narrow, and points directly 

 to the front. In all, the elements of the pectoral arch or shoulder- 

 girdle are very much alike, though the individual bones of the 

 hybrid rather more closely simulate the corresponding ones in 

 my skeletons of the Prairie Hens. More particularly is this the 

 case in the form of the much expanded hypocleidium of the os 

 furcula, this expansion being considerably narrower antero-pos- 

 teriorly in Pcdioctctcs than it is in Tympanuchus or in this 

 hybrid. For the diameter indicated, in the last two it measures 

 12 millimetres, while in the Sharp-tailed Grouse it measures but 

 9 mm. or less. 



Excepting in the matter of size, the characters of the femur of 

 this hybrid Grouse are in exact agreement with those of the 

 femora of the parent species. We note, however, that the calibre 

 of its shaft is relatively, as well as actually, stouter than it is in 



1 Loc. cit. Plate XII, figs. 83, 84. 



