88 BREWSTER, Descriptions of New Birds. [April 
My series of this form is large, comprising no less than sixty- 
five specimens from Lower California, and thirteen from Alamos 
in western Mexico.. Among these there is surprisingly little indi- 
vidual variation in respect to the characters above pointed out, 
although the general coloring varies considerably with season. 
Autumnal birds have the upper parts faintly olivaceous, the under 
parts suffused with pale yellow, but the deepest colored specimens 
do not at all closely resemble the much darker and browner &. 06- 
scurus. The peculiar coloring of the under mandible is not subject 
to seasonal variation but, on the other hand, it is not uniform, 
some specimens having only the extreme tip dark, while in 
others the yellowish is confined to the basal fourth of the mandible. 
Only one bird inthe entire series has the lower mandible uni- 
colored (light brown) from base to tip. On the whole the gen- 
erally large size and especially long, slender bill are probably the 
best characters of &. gréseus. 
Turning now to &. obscurus, 1 find—among some fifty speci- 
mens from various parts of the western United States—much vari- 
ation in coloring and excessive variation in the size and shape of 
the bill. Examples from southern Arizona and New Mexico are 
the lightest and grayest, and have the longest and narrowest bills. 
In some the bill is colored as in /. grzseus; indeed several ap- 
proach the latter very closely and are probably referable to it. 
Nevertheless #. grcsews seems to be quite as distinct from 
EF. obscurus as is the latter from &. hammondz. Indeed the 
material before me furnishes a series, apparently unbroken and 
very nicely graduated, connecting the largest, grayest specimen 
of grzseus on the one hand, with the smallest, most olivaceous 
examples of hammondi on the other, the middle links of the 
chain being the specimens referable to obscurus. In almost any 
other group—save perhaps the Juncos—such a series would be. 
conclusive proof of specific identity; but among Hmpcdonaces 
forms shown by differences of habits, color of eggs, etc., to be 
perfectly distinct, are so often difficult of separation in the dried 
skin that ornithologists have learned to regard extremely slight 
peculiarities of form or color as good specific characters. Hence 
it is probably wisest to let the birds just mentioned stand, at least 
for the present, as full species. 
In this connection a question of synonymy occurs, vzz., the possi- 
ble necessity of using the name odscurus for the bird which I have 
