Henshaw on the Species of the Genus Passerella. 7 
specimens of townsendi equalling) the tail ; while in schistacea 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 , w T ith its wing nearly 
equal to tail, evidently marked the first step towards schistacea , in 
which the tail becomes the longer, a tendency carried still further 
in megarhyncha. 
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. erythrophthalmus. 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) fide Kidgway. 
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. 
