1^8 Ridgway, Geographical Variation in Sialia mexicana. I Apr n 



Adult female in spring {No. 41,230, Ft. Whipple, Arizona, April 29, 

 1S65; E. Coues) : Practically identical in coloration with No. 82,590, 

 Marin Co., California (described previously), but buffy cinnamon of 

 breast tinging chest and throat, instead of being sharply defined against 

 the clear light drab-gray of chest. Total length (skin), 6.30 (6.60 before 

 skinning); wing, 4.15; tail, 2.47; exposed culmen, 0.45; tarsus, 0.75; 

 middle toe, 0.60. 



Adult female in autumn (No. 69,216, Apache, Arizona, Oct. 24, 1874; 

 H. W. Henshaw) : Practically identical in coloration with No. 2949, 

 described on page 157. Total length (skin), 5.95; wing, 4.00 ; tail, 2.50; 

 exposed culmen, 0.43; tarsus, 0.75; middle toe, 0.55. 



In adult males of the Coast form, the blue varies from the light 

 azure hue of the type to a clear purplish smalt blue in No. 21,425, 

 Ft. Crook, Cal. (October 22). Both these extremes are very 

 unusual, however, no other examples in the entire series 

 approaching either of them very closely. Among the remainder, 

 the blue ranges from a hue intermediate between smalt and ultra- 

 marine to pure ultramarine. 



The only specimen which, at first sight, seems to have no 

 chestnut on the back is No. 13,281, Genoa, Nevada (June 20) ; 

 but close inspection discovers traces of chestnut in the form of 

 edgings to some of the feathers on each side of the upper back. 

 This example also has the blue of the chest extended to the belly, 

 completely dividing the chestnut of the breast. It is also unusu- 

 ally large, the wing measuring 4.35, the tail 2. So. It thus ap- 

 proaches in all these characters S. m. anabelce, but may be at 

 once separated by the much more slender bill. Specimens in 

 perfect adult spring plumage (as No. 82,589, Nicasio, California 

 (April 11) show little if any difference in intensity of color 

 between the blue of the throat and chest and that on top of the 

 head. 



Adult males of the Rocky Mountain form average perhaps a 

 little more purplish blue than the coast form, the extremes being 

 cobalt and smalt-blue, the average hue being intermediate 

 between smalt and ultramarine, but nearer the former. Several 

 males of this form show very distinct black mesial streaks on the 

 upper tail-coverts (e. g., No. 105,258, El Paso Co., Colorado, 

 March 30, and No. 41,227, Ft. Whipple Arizona, April 19). 



I have been unable to detect any difference between females of 

 the two forms. There is a considerable amount of individual 



