OSTEOLOGY OF BIRDS 



31 



of the rib at its extremity lengthens as we pass backward toward 

 the pelvic end of the body, in due proportion does the one bearing 

 the tnberculum shorten, until in the latter we have the transverse 

 process of the vertebra, in the last dorsal, resting for the outer third 

 of its length against the true neck of the rib opposed to it, and the 

 tubercular pedicle has become sessile with the body of the rib. 



The ribs of the Cathartidae, or such of them as are found in the 

 dorsal division of the spine, are very broad throughout their entire 

 lengths, the broadest part being found at their superior thirds ; this 

 transverse compression gives rise to sharp anterior and posterior 

 borders, and long elliptical facets, placed longitudinally below for 

 the sternal ribs. 



All of the dorsal ribs support epipleural appendages in the Ca- 

 thartidae, and they are anchylosed to the posterior margins of these 

 bones, below the middle of their shafts. We believe that this is the 

 case in the vast majority of the Falconidae, including the Old 

 World vultures. These unciform offshoots of the ribs are very 

 widespreading and prominent, more so among the American vul- 

 tures than in any of the hawks or eagles, and as a rule overlap 

 the rib immediately behind them, but never two consecutive ones ; 

 as in -some birds. 



There are some very interesting and distinctive differences be- 

 tween the ribs of the Cathartidae and those bones as they occur 

 among the Falconidae and the vulturine Raptores of the continent; 

 these differences are principally due to the various patterns as- 

 sumed by the epipleural appendages now under consideration, as 

 well as changes in form of the bodies of the ribs themselves. 



Our figures, herewith presented, exhibit these differences so well, 

 that it seems to render any special description unnecessary. Especial 

 attention, however, is invited to the form assumed by the epipleural 

 process, and the relative width of the body of the rib. They attest, 

 even in' this minor character, to the affinities of the various forms 

 compared. Neophron practically agrees with the Falconidae, and 

 the Cathartidae exhibit a family character peculiar to themselves. 

 Attention is particularly invited to the descending part of the epi- 

 pleural appendage in our vultures, and this is most strongly marked 

 in the ribs from the middle of the dorsal series; it being entirely 

 absent in the Falconidae and their allies. 



The first dorsal rib in Gypoger anus serpentarius 

 bears no epipleural appendage ; in the second it is broad and short, 

 with a minute descending process below, very close to the margin 

 of the rib; in the third this unciform appendage is long and narrow, 



