522 SwARTH, California Forms of Psaltriparus. [oct. 



Sierras, but little less distinct than in a single specimen from the 

 Warner Mountains (no. 15297). In the Carroll Creek bird the cap 

 is not so obvious, but might become more distinct with the comple- 

 tion of the molt. The measurements of both these birds coincide 

 with those of phimbcvs rather than caUfornicus. 



It will be noted that these specimens, of intermediate nature, were 

 taken at the extreme southwestern limits of the range of Psaltri- 

 parus plu7nbeus. The ranges of this species and P. minimus caU- 

 fornicus adjoin at this point, typical examples of the latter being 

 taken at Carroll Creek, at the same time and place with the aber- 

 rant specimen of plumbcus described above. It will also be noted 

 that one specimen of caUfornicus from the Warner Mountains, pre- 

 viously described, shows a decided leaning toward the characters of 

 pluvibeus. In other words, at the one point where the ranges of 

 Psaltriparus plumbeus and P. minimus caUfornicus are known to 

 touch, and at one other point, an extreme eastern outpost of the 

 latter subspecies, we find specimens of intermediate character, with 

 difficulty referred to either one of the two. This is suggestive of 

 much closer relationship between them than has heretofore been 

 suspected, and it may be that further collecting and observations 

 in debatable territory will demonstrate the differences to be merely 

 subspecific, necessitating a return to the trinomial, Psaltriparus 

 minimus plumbeus, formerly in use. 



At present, however, the facts hardly justify such a radical step. 

 In the first place, the region of blending, even if its existence may be 

 considered as established, is obviously very narrow, while the inter- 

 mediate specimens are almost of the nature of hybrids. There is 

 no gradual change from the characters of one species to the other, 

 examples of pluvibeus from the Sierras being for the most part in- 

 distinguishable from iVrizona and Nevada specimens. It is of 

 decided interest to note the existence of these doubtful specimens, 

 as another example of the different kinds of intergradation, and 

 varying degrees of difference, to be found between what we call 

 species and subspecies of animals. 



In commenting upon P. plumbeus at the eastern border of its 

 range, where it meets P. melanotis lloydi, Ridgway (1904, p. 430, 

 footnote) remarks: "The relationship of this form to P. melanotis 

 lloydi affords a problem very difficult of solution and of exceptional 



