NATURAL SCIENCES OF PHILADELPHIA. 187 



nature of the food obtained there, &;c. I noticed nothing, however, in Labra- 

 dor, that seemed sufficient for such end. It would be interesting to have in- 

 formation upon this point from observers in the interior of Arctic America. 



If ca}icsce?is has been shown to have probably been at one time linarius, and 

 subsequently modified, as we have seen, by the operation of known laws, I see 

 no reason for supposing that /i/scwcen* is more distinct because we cannot so 

 readily trace the laws under which it has been made what it is. We have only 

 to take for granted, in this case, either a later departure from the common 

 standard, or, what is more probable, a less regular, continuous, and cousenta- . 

 neons operation of modif^'ing influences. In rufescens and holboeUi the effect 

 of these influences is as yet barely apparent ; \vl Juscescenn \l is already very 

 evident. 



In Greenland, side by side with the blanched raollipilose canescpns, we have 

 a few singular ^Egiothi. It seems as if they had sprung like offshoots from 

 fuKccscens. and there in Greenland, stationary or nearly so, and isolated, the law 

 of latitude had come into play to enlarge them; but that further interference 

 with fnscescent features had not been experienced. These ^-Egiothi, that I call 

 rostralus, are : 1, as large as, or scarcely less than canescens (about six inches 

 long) ; 2, with a bill that is even an exaggeratiou of that offuscescens, being 

 still larger, thicker, more turgid, with short plumules, and black in color ; 3, 

 with the colors of fuscescens, the heavy stripes on the side being sometimes 

 carried quite across the belly. There appear to be fewer of these than of any 

 other JEgiothits ; I have not seen a dozen in all, and none except from Green- 

 land. One or two of these are appreciably lighter than the rest, and in fact, 

 shape of bill and total size apart, rather recall dull plumaged linarius. I 

 scarcely know what to make of this form, after accounting for its size as above, 

 and prefer to leave it with this simple statement of fact. In a classificatory 

 point of view, it appears to hold somewhat the relation \o fuscesceni that canes- 

 cens (or possibly rather only holboeUi) does to linarius. Though I did not reach 

 such opinion in my monograph of 1861, I should now, in spite of its several 

 very obvious peculiarities, consider its characters, in relation to those of /««- 

 cescens or liniarius, as ofless systematic value than those of any " species " ex- 

 cept rufescens and holboeUi. The small number of specimens at my command 

 will not allow me to expose the precise degree in vrhich it graduates towards 

 fascescens ; but it is probable that some such assimilation occurs, and that no- 

 thing but the birds' i|plation in Greenland prevents them from shading insen- 

 sibly mio fuscescejis. 



lY. Perhaps the most interesting modification of JEyiothus remains to be 

 noticed ; I refer to what I call exilipes. Audubon figures it by mistake for 

 canescens, which I presume he never saw; and Elliot has recently given another 

 illustration. It is the " mealy red-poll " of American, but not of European, 

 writers. The peculiarities oi exilipes do not occur, so far as known, ia Asia, 

 Europe, or -Greenland, but they are characteristic of a large number — perhaps 

 the majority — of boreal and arctic American ^-Egiothus. These modified .S^io- 

 thi do not come so far south as linarius does ; in general they may be said to 

 be confined to British and Russian America, though some appear to occasion- 

 ally pass the northern boundaries of the United States in winter. They are 

 very generally dispersed, being contained in almost every collection sent from 

 the interior and the north-west coast, but are perhaps more abundant westward. 

 They are migratory, if irregularly so. The}- sometimes seem, judging from 

 collections, to be the only form in some localities, but more generally they are 

 associated, if not at the same season of the year, with linarius AnAfuscescens, — 

 sometimes both. It seems as if there were a wave of linarius swaying north 

 and south, between certain parallels of latitude ; another of exilipes between 

 certain higher parallels ; yet the two regularly meeting on common ground, 

 and each sending and preying still further in the direction of the other. 



The characters of exilipes are these : 1, size of linariut ; 2, colors (very 



1869.] 



