.58 



gradation versus isolation. Fo specimens in any way intermediate be- 

 tween iephrocotis (in any of its forms) and australis have been found j 

 consequently, tbey are held to be distinct specifically. On the other 

 hand, there are numerous examples intermediate in different degrees 

 (according to the individual) between tephrocotis and Uttoralis; which 

 being the case, they cannot be considered distinct species, but, on ac- 

 count of the fact that they occupy separate countries during the breed- 

 ing-season and that the intermediate specimens are found only along 

 the line of junction of these areas, they must be recognized as definable 

 geographical races. The same niaj^ prove to be the case regarding 

 Uttoralis and griseinuclia ; while, as is the case with L. australis, L. atrata 

 stands apart from the other forms. We have yet to see, however, speci- 

 mens intermediate between Uttoralis and griseinucha ; indeed, tephrocotis 

 and Uttoralis are the only forms which we are certain do intergrade. 



GEOGRAPHICAL VARIATION. 



Xo one but Mr. Allen has attempted to show a correlation between 

 the distinguishing characters of the different forms of this genus, and 

 the recognized general laws of geographical variation ;* and the few 

 remarks of this gentleman upon the subject are far from stating the 

 facts of the case. In his first discussion of the relationship of the 

 Mount Lincoln specimens (i. aiistraUs), he says: "Although these 

 birds may have been born at widely-separated localities, it seems 

 probable Ihat some of the differences whereon certain species of Leu- 

 costicte have been founded may be only individual variations. It is 

 to be noticed, however, that the amount of ash on the head and 

 the intensity of the colors vary with locality from the north south- 

 ward 5 the most southerly form having no ash on the head, the bill black 

 instead of yellow, and the red of a brighter tint from those of more 

 northern localities. The type of X. tephrocotis was a male, killed on the 

 Saskatchewan in May, in which the ash formed a narrow nuchal band. 

 In L. griseimicha, a, more northern form, the gray involves the whole 

 head and the throat; and, in L. Uttoralis and L. campestris, there is more 

 gray on the head than in tephrocotis, and they appear to be more north- 

 ern in their distribution. In view of these facts, it seems probable that 

 the Mount Lincoln specimens above described represent the smaller, 

 brighter-colored, southern race, in which the ash of the head has en- 

 tirely disappeared."— (Bulletin of the Museum of Comparative Zoology, 

 III, No. 6, July, 1872, p. 163, foot-note.) 



Eegarding the subject of individual variation, we shall say little, since 

 the immense series at our command shows that this is really insignifi- 

 cant; but, respecting the statements which follow, there is need of correc- 

 tion. There is no such variation from the north southward as that stated 

 in the passage quoted ; for the northern forms are quite as brightly 

 colored as the most southern ones, while in the gray-headed races of L. 

 tephrocotis, it is the more southern one (var. Uttoralis) which has the most 

 gray. Thus, in this latter race the throat is more or less gray, frequently* 

 entirely gray; while, in var. griseinucha, the whole throat is black ! Var. 

 griseinuclia is also much brighter-colored than its southern ally, the red 



* Consult on this subject the following authorities: 



Baikd, American Journal of the Arts and Sciences, XLT, March and January, 1866. 

 Allen, Bulletin of the Museum Comparative Zoology, Cambridge, ii, 1871, part iii. 

 ElDGWAY, American Journal of the Arts and Sciences, IV, December, 1672, p. 454 ; V. 

 January, 1873, p. 39, — American Naturalist, VII, September, 1873, p. 

 COUES, American Naturalist, VII, July, 1873, p. 415. 



