?l6 Oberholser, The Mexican Forms of Certhia. I Oct 



crissum pale, tawny ochraceous, many of the feathers tipped with white ; 

 remainder of lower parts grayish white with, posteriorly, an almost inap- 

 preciable rusty tinge. 



This subspecies may, by its much darker color above, be at 

 once distinguished from any of the other forms of Certhia occur- 

 ring in the United States, and requires comparison with only 

 C. familiaris alticola from southern Mexico and Guatemala. From 

 this it differs most tangibly in its much less rufescent tint above, 

 the ground color of the plumage being clove brown instead of 

 sepia ; the streaks on head and back are much more clearly 

 white and more sharply defined, and on the former somewhat 

 larger. All the other light markings are more nearly pure white, 

 usually lacking in a large degree the rufescent tinge seen in 

 alticola. The lower parts are much lighter in color, being pure 

 white anteriorly, and light grayish posteriorly, instead of dull 

 rufescent gray with an admixture of rusty. The color of the rump 

 apparently does not present a constant character, as some speci- 

 mens from Arizona have this part fully as light as the Guatemala 

 birds. The length of the bill, which was mentioned by Count von 

 Berlepsch as diagnostic, cannot be relied upon to separate the two 

 races, as may be seen by reference to the measurements given in 

 the present paper. 



Specimens of albescens from Chihuahua, Sonora, and Arizona 

 are practically identical in coloration ; but none from other locali- 

 ties have been examined. 



Certhia familiaris alticola (Miller). 



Certhia mexicana Gloger, " Handbuch, 1834, 3S1 " (part). 



Certhia familiaris var. mexicana Baird, Brewer & Ridgway, Hist. 



North Am. Birds, I, 1874, 12S (part). 

 Certhia familiaris alticola Miller, Auk XII, April, 1895, 186 (part). 



Chars, subsp. — C. familiari albescent! affinis, sed capitis et nuchae 

 striis angustioribus, corpore supra nmlto rufescentiori, subtus magis sor- 

 dido, plus minusve ferrugineo tincto. 



Al., sS-67 (64.8) mm.; caud., 55-66 (61. 2) 1 mm.; exp. culm. 12-16 

 (14.2) mm.; tars., 14-16 (14.7) mm. 



1 Excludes five specimens which have the tail much worn or otherwise 

 imperfect. 



