764 GEOLOGICAL SURVEY OF THE TERRITORIES. 
oceurs on any of the sacral ribs. We know of no instance among the 
Falconide where it ever assumes such a form; and its outline as seen 
in Neophron (0) leads us to believe that this is only an additional ex- 
ample where these birds depart from the Cathartide and tend towards 
the Falconide. 
The first dorsal rib in Gypogeranus serpentarius bears no epipleural 
appendage; in the second itis broad and short, with a minute descend- 
ing process below, very close to the margin of the rib; in the third this 
unciform appendage is long and narrow, and is in contact with the rib 
for its entire length, sloping away below; in the last dorsal it appears 
only as an increased widening of the rib for a certain distance along the 
usual site of its occupancy. Sternal ribs that in descending meet the 
dorsal ribs are, like these bones, strong and robust; they possess quite 
extensive quadrate facets for sternal a: ticulation at their lower ends, that 
when placed in sitw in the skeleton cause these bones to be turned out- 
wards, so that their anterior faces are visible from a direct lateral view. 
Their posterior ends are progressively from before, backwards, curved 
in such a manner as to preserve the oval form of the chest walls, and 
are very much dilated as we proceed in that direction; at. their distal 
extremities they support the usual facets for the vertebral ribs. In the 
Secretary Vulture they become very much compressed from side to side 
as we examine them successively in the order referred to, and in this 
course, too, in some of the Falconida, they become curved in an antero- 
posterior direction, the concave margin being in front. In these birds 
and in our specimen of Neophron the sternal ribs are seen to be much 
slenderer than corresponding bones in the Cathartide. 
Additional protection is afforded the contents of the thoracic and ab- 
dominal cavities by ribs descending from the sacral vertebree; by free 
sternal ribs in other species, and by the meeting and articulation of both 
in others. To complete the description of these important and serial 
auxiliaries to the stability of the chest walls, we will say what we have 
observed in regard to these sacral ribs here, so that we will be left com- 
paratively free to describe that bone as a unit. 
Sarcorhamphus gryphus has three of these ribs on either side; the first 
two pair support epipleural appendages and articulate with the sternum 
through the agency of well-developed sternal ribs. The last pair are 
devoid of the unciform projections, and their sternal ribs in turn articu- 
late by their distal extremities and a small portion of their distal and 
anterior margins along the posterior borders of the sternal ribs in front 
of them, their points coming within about a centimeter of the costal 
border of the sternal body on either side. We believe, after an exam- 
ination of such parts of our skeleton of Pseudogryphus as refer to this 
region, that the arrangement will be found to be the same as we have 
just attributed to the South American Condor. Gyparchus possesses two 
pair of these ribs, both articulating with the sternum by sternal ribs 
that are the largest and longest of the series. The first pair have unci- 
form processes. Sometimes in this species an additional rudimentary 
pair are found to exist, and belong to the next vertebra beyond, but all 
the distinctive characters of the upper part of a rib have been absorbed 
by the under surface of the illium, so that this pair almost has the ap- 
pearance of being offshoots from the ossa innominata. : 
In Cathartes aura we discover two pair, the first connecting with per- 
fect sternal ribs coming from the sternum below, and support epipleural 
appendages; the last are without them, and otherwise behave as we 
described the ultimate pair in Surcorhamphus. Passing to Catharista, 
we find the same arrangement present as in O. aura, but in addition a 
