82 RiDGWAY on the American Vultures' 



Pseudogryphus californianus. This species appears to 

 have become excessively rare in Cahfornia, having been nearly, if not 

 quite, exterminated in many parts of the State, through the agency 

 of poisoned carcases exposed for the destruction of bears and 

 wolves (c/'. Henshaw, Ann. Rep. Geog. Surv. W. 100th Merid., 1876, 

 p. 265). It may not, perhaps, be generally known, — at least the 

 fact has been almost wholly overlooked by authors, ■ — -that this spe- 

 cies is fully the peer of the Condor in size, the length of the wing 

 and tail averaging even decidedly greater. It is not, however, 

 quite so strongly built, the beak and feet being proportionately 

 weaker. Apropos of the wide disagreement of authors as to the 

 alar expanse of the Condor, I have been led to try a very simple 

 method of determining what should be the stretch of wing in that 

 species and P. californianus, with a result which is undoubtedly 

 approximately correct. This method is based upon measurements 

 of the wing bones of these two species and Cathartes aura, and the 

 application of the " Rule of Three," as follows. 



The maximum length of wing in C. aura is 23 inches, the hiimerus 

 measuring 6.00 inches, and the ulna and radius 7.25 inches, making 

 the total length of one outstretched wing 36.25 inches. The maxi- 

 mum alar expanse of this species is 6 feet, or 72 inches. In S. 

 gryphus and P. californianus the maximum total length of wing is 

 55.50 and 58.25 inches, respectively. Therefore, assuming that the 

 primaries have about the same proportionate length in the three 

 species, we have, by applying the aforesaid rule, the following 

 result : — 



Sarcorhamphus gryphus (length of outstretched wing, 55.50 inches). 



36.25 : 72 : : 55.50 : 110.23 = 9 feet 2 inches. 

 Pseudogryphus calif or nianus (length of outstretched wing, 58.25 in.). 



36.25 : 72 : : 58.25 : 115.65 = 9 feet 8 inches. 



Allowing for individual variation in both species, the average 

 alar expanse of each may be set down at about 9 feet, P. cali- 

 fornianus, at least, perhaps sometimes reaching 10 feet, while it is 

 quite certain that the largest individuals of either would not much 

 exceed, if indeed they reach, an extent of 10| feet. 



For sake of comparison I give below measurements of certain 

 bones of S. gryphus, P. californianus, and C. aura, taken from fully 

 adult examples of each. 



