Henshaw on the Species of the Genus Passcrclla. 5 



mandible in typical megarliyncha is of a quite characteristic bluish- 

 white, but in these specimens it is of a decidedly yellowish cast,* 

 very much as seen in schistacea. A similar tendency in them to 

 approach the light ashy coloration of schistacea is also to be noted. 

 By means of these and other specimens we have no difficulty in 

 forming a very complete chain from the one extreme to the other, 

 and hence we consider the two are to be distinguished only varie- 

 tally, whatever may be their relations to the others. 



Of megarhyncha it is to be said that the individual variation is 

 very great, being much more marked than in any of the three 

 others. Though in its extreme condition it is certainly one of the 

 most, perhaps the most, noteworthy of the four birds, its characters 

 are so very inconstant that unless taken from the same locality it 

 is not easy to find two specimens that exactly agree, the variation 

 being especially well marked as to size. In a series even from the 

 same neighborhood the variation is apt to be very considerable, 

 more so, I think, than is the case with any other bird I am ac- 

 quainted with. As this variety is probably a resident, at least in 

 much of the region inhabited by it, it is not easy to understand 

 this tendency in individuals to vary to so great an extent. On the 

 other hand, its claim to similar recognition as the others is seen in 

 the fact that its habitat is distinctly marked from that of its con- 

 geners, and that within its own area no specimens occur which are 

 not sufficiently characteristic to be readily referable to it. As to 

 the relative size of wing and tail in the two forms, the individual 

 variation is never sufficient to alter the proportion, the tail being 

 always in excess of wing. 



Leaving now, for the moment, the two forms (schistacea and 

 megarhyncha) just considered, and taking up the two remaining 

 members of the group (iliaca and toumsendi), we note, first, that 

 their habitats are, in the extreme northwest, in close relation, — 

 iliaca being one of the several eastern birds that in the far north 

 span the continent, and reach the Pacific Ocean in Alaska. Town- 

 sendi is a Pacific-slope form, being found in its typical condition 

 from the Columbia River region north to Sitka, Kodiak, etc. 

 Whether the habitats of the two actually join is not at present 



* Mr. Ridgway informs me that specimens collected by him in this vicinity 

 in spring show no trace of yellow, but have the typically bluish-white under 

 mandible. 



