No. 2.1 SnUFELDT ON NORTH AMERICAN TETRAONID^. 343 



being struck with these marked departures from the common type. 

 There is one other Grouse that afi'ects this style of pelvis, and that is 

 Fedicecetes, and the attempt is not a had one. The principal points 

 wherein the Sharp-tailed Grouse has failed to make a perfect imitation 

 of the unique pelvis of his ideal are, the ilia have failed to produce such 

 ponderous overhanging lateral tlaps, that neaily shut out from view the 

 ischiadic foramen on either side. Again, these bones in Fedicecetes meet 

 the sacral vertebrae for their entire length internally ; and in this bird, 

 too, the pubic elements often unite all along the inferior borders of the 

 ischia. This does not occur in the Pinnated Grouse ; otherwise the bones 

 are very similar and marked exceptions to the general pattern of the 

 other members of this subfamily. 



After examining a large number of the i^elves of our Grouse, and 

 noting their capacious cavities and great width from side tQ side, one 

 cannot help but be surprised at the great change in outline, on turning 

 to these bones as they are found among the Partridges. 



As a rule in these birds, the pelvis is elongated and unusually narrow, 

 though the drooping ischia behind give it additional depth in its more 

 posterior parts; the pubic bones are turned up behind after they extend 

 beyond the elements above them, and the lateral walls formed by the 

 ilia are, just beyond the acetabula, almost vertical; in fact, one would 

 almost suspect the pelvis of the common Virginia Partridge as belong- 

 ing to the skeleton of some variety of Curlew, had he not been sure of 

 the owner. This apparent departure from the more general model of 

 this bone in Gallinaceous Fowls, however, is not nearly so decided in 

 other varieties of the Odontophorince, as for instance in Lopliortyx cali- 

 fornicus, and a very good drawing of the pelvis of this bird can be seen 

 and studied, in Mr. T. 0. Eyton's Osteologia Avium, London, 1867, Plate 

 22, figs. 1, 1, 1, 1 ; three of the figures here cited, however, are for the 

 palatine bones, inferior view of sternum, and anterior and posterior 

 views of the tarso-metatarsus. We have carefully compared the diam- 

 eters of these representations with the skeletons of the species in ques- 

 tion, and find them quite accurate. 



The femur in the young chick of Centrocercus is less than demi-de- 

 veloped; above, the head is almost entirely cartilage, while below the 

 condyles are very indistinct and the bone bears no signs of pneuma- 

 ticity. In a few weeks, however, these points rapidly exhibit them- 

 selves: a rounded trochanterian ridge is thrown out; the head essays to 

 assume its sphericity; the condyles become evident; the fibular groove 

 appearing last of all and about the same time with the vascular foramen 

 or medullary orifice at junction of upper and middle thirds. Eegarding 

 this bone in a fine old ^ from Cupidonia, and comparing it with others, 

 we find that it is remarkably well balanced in point of length and gen- 

 eral development. 



The trochanterian ridge is markedly prominent and arches over the 

 articular facet for the ilium ; the neck is distinct and makes an angle 



