_SHUFELDT.] OSTEOLOGY OF THE CATHARTIDA. 165, 
pair of rather long styliform rudimentary ones are found, with their 
capitula, tubereula, and necks absorbed as we saw them when they 
occurred in Gyparchus, though evidently belonging originally to the 
next vertebra in order. So that among the Cathartide the variations 
observable among the plans for the sacral ribs resolve themselves into 
the following four classes: They vary as to the number of pairs; as to 
the presence cr absence of rudimentary ribs; as to the method of ar- 
ticulation of the last pair of sternal ribs, whether these descend to 
the sternum or articulate along the posterior border of the pair in ad- 
vance of them, thus constituting what might almost be termed ‘float- 
ing sternal ribs”; and, finally, as to the arrangement of the unciform 
processes. 
Turning to such specimens of the Vultures of the Old World as we 
have been able to learn anything about in this regard, we perceive at 
once that we have an entirely different set of ‘plans of arrangement” 
presented tous. In Neophron percnopterus we have a free pair of sternal 
ribs that articulate with their anterior ends on facets in the costal bor- 
ders of the sternum, just as any other pair of the series do; no evidences 
of a corresponding pair of sacral ribs descend to meet them. 
Mr. Lueas tells me that he found in Vultur cinerea and Gyps ben- 
galensis that the ultimate pair of sternal ribs were still free as we found 
them in Neophron, but that the anterior extremities articulated with 
facets in the posterior margins of the next pair of sternal ribs beyond 
them. He further says that in Otogyps calvus “a very small floating 
rib is attached throughout its entire length to the last articulated sternal 
rib.” This no doubt « occurs on both sides, and is the same condition as 
we find in Gypogeranus, only the rib is longer in this latter vulturine 
Falcon. Cases of asymmetry no doubt occur among many or all of 
these various arrangements, as, for instance, in the skeleton of Alicras- 
tur brachypterus that we have before us we find that on the left side six 
sternal ribs spring from the sternum, while on the right there are only 
five, the last or sixth one articulated with the posterior border of the 
sternal rib beyond it. 
Of the scapular arch, ee. and pectoral limb.— As in the majority 
of the class Aves, the scapular arch of the Cathartide consists of its 
pair of scapule, its pair of coracoids, and its furculum, or the united 
clavicles. This group of bones enjoys the usual amount of indepen- 
dence that we find in nearly all birds, in being distinct from each 
other and from the sternum. There is a very great similarity, both 
in outline and general appearance of this arch as it is found among 
the Cathartide, and to this we may add that when the bones forming 
it are in situ in the articulated skeleton they present a pattern that 
not only possesses a common resemblance, but is peculiar to the 
family, and differs very decidedly trom the Vultures of the Old World 
and from the Falconide. We find in our present subjects that the 
sternal extremites of the coracoids are very much expanded in a 
transverse direction, that they touch each other, mesiad, When articu- , 
lated in the sternal grooves or beds designed for them. These dilated 
ends are scooped out on their posterior aspects where the pneumatic 
foramina occur, and roughened, while in front the surface is smooth, 
convex from side to side, and continuous with the general surface of the 
shaft. The inferior side is occupied for more tian its inner half by the 
facet for articulation with the sternum; this is broadest mesiad, nar- 
rowing in each bopve as we proceed outwards. The outer angle is trun- 
cate and presents an upturned tip of bone, and a face that is directed 
outwards. Very little shaft can be boasted of by these bones, for no 
