Henshaw on the Species of the Genus Passerella. 7 



specimens of townsendi equalling) the tail ; while in schisfacea and 

 townsendi the tail is very considerably in excess of the wing. The 

 importance which I was at first disposed to attach to these differ- 

 ent proportions was somewhat modified upon ascertaining that in 

 respect to proportion of these parts townsendi, with its wing nearly 

 equal to tail, evidently marked the first step towards schisfacea, in 

 which the tail becomes the longer, a tendency carried still further 

 in viegarhyncha. 



One curious and to me unexpected fact brought out by these 

 measurements is that, not only does the tail become longer in the 

 three western varieties, — a variation well shown in other species 

 whose habitat extends from the eastern into the western province, 

 — but also the wing is found to be actually shorter; so that the dif- 

 ferent proportions which ensue result from two causes : first, actual 

 increase in the length of tail ; second, actual decrease in the length 

 of wing. I am not aware that this fact has been noted in the case 

 of any other western bird, though I find a similar but slight ten- 

 dency in this direction in the Pipilo var. megalonyx, the western 

 form of the P. erythrophthabmis. A careful examination of other 

 species may reveal a similar tendency. 



By the above arrangement the four forms will require to stand 

 as follows : — 



Passerella iliaca (Merr). Habitat, Eastern Province of North America. 

 Breeds from British America northward ; across to mouth of Yukon. 

 In migrations to eastern edge of great plains ; occasional in spring in 

 Colorado (Maxwell) ^(Ze Ridgway. 



Passerella iliaca townsendi (Aud.). Habitat, Pacific Province. 

 Breeds in Northern Sierras ; Southern California in winter ; confined to 

 western slope of Sierras. 



Passerella iliaca schistacea, Bd. Habitat, Middle Province, re- 

 stricted by western edge of plains and eastern slope of Sierras ; a rare 

 straggler in Kansas and California in fall. 



Passerella iliaca megarhyncha, Bd. Habitat, southern Sierras, 

 eastern as well as western slope. Probably resident wherever found. 



