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University of California Publications. [Geology 



Both exhibit a marked degree of flattening of the bone, a char- 

 acter found also in Cathartes, Catharista and Gypagus. 

 Cathartes and Gypagus show perhaps the extreme of this condi- 

 tion, Gymnogyps occupies an intermediary position, while 

 Sarcorhamphus and Catharista display it to a minimum degree. 

 The deep furrowing of the anterior face of the shaft is likewise 

 a common character and a character which somewhat closely 

 parallels the preceding one in its variation with the different 

 genera. Both characters remain quite constant for a given 

 species if Cathartes and Gymnogyps may be considered as rep- 

 resentative. Width of shaft in relation to width of extremeties 

 seems to vary perceptibly with age. The articular surfaces 

 seem to attain full size while the shaft is yet comparatively 

 slender. 



An examination of representatives of the five genera of Recent 

 eathartids, which ornithologists group into two subfamilies, shows 

 a greater homogeneity of characters of the tarsus than is dis- 

 played by the series of twenty-four condor-like tarsi from the 

 asphalt beds. Even casual examination shows that this series of 

 fossils falls easily into four distinct groups. The group contain- 

 ing the largest number is considered to be specifically identical 

 with the Recent Gymnogyps calif or nianus. The second series, 

 consisting of two specimens, compares most nearly with Sarcor- 

 hainph us, to which genus it is tentatively assigned. In the absence 

 of larger series for the study of variation in either form, the 

 entire significance of the differences between the fossil and the 

 Recent forms of Sarcorhamphus is hard to determine. It would 

 seem best under the circumstances to consider them of no more 

 than specific importance. The other two groups of the series 

 show such extensive divergence from all of the known genera 

 as to make the establishment of new genera for their reception 

 the only consistent step possible. 



GYMNOGYPS CALIFOBNIANUS (Shaw). 

 A series Of fourteen specimens of the tarsus represents the 

 existing Californian species. In this series the homogeneity is 

 remarkable and altogether sufficient to obviate the necessity of 

 a greater series of Recent skeletons. The series is assigned 



