680 GEOLOGICAL SURVEY OF THE TERRITORIES. 
ture towards the pelvic extremity of the body. To compensate, or rather 
what really gives rise to to this, as far as the bird’s osseous structure is 
concerned, among other things, is a lengthening of the diapophyses as 
we proceed in that direction. The ribs also become longer; the xiphoidal 
forks of the sternum flange outwards. So, too, we find a corresponding 
shrinking of the tubercula on the dorso-vertebral pleurapophyses, and 
a stretching of the correlative necks, so that the capitula may reach the 
facet intended for them on the vertebre. 
The vertebral ribs as seen in the Grouse are pneumatic, the foramina 
being found on the posterior aspect of these bones immediately below 
the tubercles, sheltered by the flattened bodies as they dilate in that 
region. 
As in nearly all birds, these ribs are compressed from within outwards, 
and in Centrocercus are wider below the uncinate processes, contract- 
ing as they meet their sternal ribs. In these birds, too, the epi-pleural 
appendages are firmly knit to the body of the rib—though in Bonasa, La- 
gopus, and Canace they may be easily detached, leaving behind them in 
each case a Shallow concave facet. In the last dorsal rib this append- 
age is the smallest, and is directed upwards nearly parallel with the body 
of the rib, and sometimes (Centrocercus) the edge of its rib swells out to 
meet its apex above; and this may have been the method by which the 
unique and remarkably striking uncinate appendages were formed in 
Cupidonia, a bird that constitutes itself an exception among the North 
American Grouse in this respect (Pl. XI, Figs. 79, 80), where not only 
the vertebral ribs are unusually broad, but their processes much more 
so, being great, odd, quadrate and compressed plates confluent with the 
body of the rib, and only rarely condescending to be weakened by the 
merest apology for a foramen to exist in them, asin Fig.80. The Sharp- 
tailed Grouse appears to come next in approaching this state of affairs; 
it, too, invariably developing more or less expanded ribs. The only 
sacral pair of pleurapophyses conform to the general shape of the series 
to which they belong, and never support epi-pleural processes. 
These bony protectors of the thoracic parietes were found to be 
exceedingly delicate in specimens of Bonasa kindly sent me by Leslie 
A. Lee, Esq., of Brunswick, Me. 
Four hemal ribs ascend from the costal borders of the sternum to 
meet the dorsal pleurapophyses in arthrodial articulations above the 
mid-horizontal plane of the bird’s body. Asis usual, their sternal ends 
are twisted so that the facets are situated transversely, while the upper 
extremities are broad and flat, particularly in Cupidonia and Pediecetes. 
The first pair are generally in advance of the others, and insert them- 
selves higher up on the costal processes: The pneumatic foramina for 
these bones are to be found just above their transverse facets anteriorly. 
The extremities of the hemapophyses of the sacral ribs meet the pos- 
terior borders of the hemal ribs of the last dorsal pair usually about. 
we junction of their middle and lower thirds of the bodies of these 
ones. 
The distal or upper extremities of these, the last pair of hema- 
pophyses, are sometimes very much expanded, and in a specimen of 
Centrocercus, 2, asmall bit of bone has been superadded, simulating an 
additional hemal spine on either side, as if anticipating the descent 
of another pair of sacral ribs to protect this otherwise feebly guarded 
region of its owner’s anatomy. 
The short pair of xiphoidal processes overlap the ultimate sternal ribs 
of all the Grouse and Quails, on either side, as do the ilia the sacral pleu- 
rapophyses above. 
