MUSEUM OF COMPARATIVE ZOOLOGY. 327 



tail, in specimens of the same variety, was much . greater than I had ex- 

 pected to find"; a result* which indicates how unreliable such fea- 

 tures are as specific distinctions, as I have already repeatedly remarked, 

 and also, of course, the fallacy of the belief, so generally held, that they 

 are really among the most trustworthy.* After detailing some of the in- 

 stances of variation in this respect in the specimens in que.-tion, he makes 

 the following remarks on variations in other characters : " The variation 

 in the number and shape of the tarsal scales is considerable, as is usual in 

 birds of this order. The development of the festoon of the lower edge 

 of the upper mandible, one of the principal generic characters, f varies par- 

 ticularly in B. montanus, the series of which is the largest, from a sharp, 

 almost tooth-like process to an entire absence ofit."% 



Dr. Bryant described each of the so-called species of the later authors, 

 and generally several authentic specimens of each, showing the variations 

 of color they present. B. montanus is the so-called " western red-tail," 

 replacing, it is supposed, B. borealis in the western half of the continent, 

 and differing from it in the main only in being more rufous or brighter 

 colored. Some specimens, however, from California and Oregon are not 

 appreciably different from others from the Atlantic States, and among 

 them is one received at the Museum from the Smithsonian Institution 

 labelled " B. borealis." B. calurus differs from these in being much darker 

 throughout, and especially below. It has, however, according to Dr. 

 Bryant, two varieties, one of which is much darker than the other. The 

 B. Harlani of Cassin, Dr. Bryant says, "resembles very closely the dark 

 variety of calurus, with the exception of its tail, which resembles mon- 

 tanus." Respecting the single known specimen of B. Coope.ri, he says 

 there is nothing in its coloration M that would make the supposition of its 

 being a variety of montanus improbable." The tail presents the greatest 

 dissimilarity and "has very much the appearance it would have in a semi- 

 adult of this species, if the color were partially washed out.' The tarsus, 

 though long, he says is not longer than in some specimens of montanus ; 

 but observes that the scutellation of the tarsus presents certain peculiar- 

 ities not seen in the others, there being but two rows of lateral scales in- 

 stead of three or four, and two more than the usual number of transverse 

 scales. § In respect to these supposed species he then observes : " After 



* See the remarks on this point in Part III. 



t The italicizing is my own. 



\ On differences of this kind the several supposed species of the B. borealis group 

 have been arranged in different subgenera .' 



§ Since writing the above I have learned from Professor Baird that he is inclined to 

 regard this specimen as " only an Archibuteo ferrugineus without feathers on the tarsus; 

 at any rate, hardly a species." It is hence omitted in Cooper and Bairds " Orni- 

 thology of California," which has just appeared. 



