1885.] PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



37 



although the question of habitat was still involved in much uncertainty. 

 The matter therefore remained quiescent until a colored plate of Buteo 

 solitarius, Peale, a Sandwich Island species, published with the rejjort 

 on the birds of the Challenger Expedition (Zoology', vol. ii, Viut 

 VIII, Eeport on the Birds; 1881), struck me as bearing a very remark- 

 able resemblance to the light-colored example of Onychotes gruheri. 

 This renewed my suspicious, and led to the further investigations on 

 which this paper is based. The type of B. solitarius, belonging to the 

 Philadelphia Academy of Natural Sciences, was, through the courtesy 

 of the officers of that institution, borrowed for compiirison, and I am 

 thereby enabled to offer the following remarks as throwing more light 

 upon the subject. 



I. The plate of B. solitarius in the report of the "Challenger" Expedi- 

 tion, the description there given of the same specimen, and that of an- 

 other example forming part of the same collection given by Mr. Gurney 

 on pp. 141, 142 of his "List of the Diurnal Birds of Prey" {ISS-i), agree 

 far more closely tcith the light- colored example of " Onychotes gruherV than 

 with tlie type of B. solitarius. In fact, the plate referred to is in some 

 respects a better representation of the Onychotes than that of the latter 

 given in the Ibis ! 



II. There being a very close correspondence in all essential characters 

 between the two "Challenger" specimens of B. solitarius and the two 

 examples of 0. gruheri, scarcely any doubt can exist as to their specific 

 identity, whatever may be their relationship to the true B. solitarius. 



JII. The type specimen of B. solitarius, while differing considerably 

 in plumage and slightly in proportions from any of the four examples 

 referred to above, is yet not sufficiently different to preclude the possi- 

 bility of specific identity ; while, on the other hand, the many points 

 of similarity strongly suggest the probability of such relationship.* 



Waiving the question of the localities where the examples of Onychotes 

 gruheri were obtained, I think that the above evidence will justify the 



* The measurements of the five known species Q,re as follows : 



Measurements of No. 2 are from the '• Challenger" report, cited .ibovc, and those of No. 3 from Mr. 

 Gurney 's " List of the Diurnal Birds of Prey." 



The type of O. gruberi is probably a male, and is evidently a young bird. This specimen and the 

 type of B. solitarius probably represent the dark and light extremes of plumage, respectively. 



