54 
BULLETIN OF THE NUTTALL 
third abruptly larger ; the fourth interniediate in length between the third 
and fifth. Entire upper parts to the tail golden-green. 
Some time since my attention was attracted by a specimen of the 
above-described bird, in the collection of Mr. William Brewster, 
which had been received from Mr. C. A. Allen, of Nicasio, Califor- 
nia, the locality where it was taken. Experience in the interior, 
especially in Arizona, had afforded opportunity for the examination 
of hundreds of the Selasphorus rufus, and this specimen, an adult 
male, differed so decidedly from any I had ever seen that I was led 
to the belief that there might be on the west coast a variety pecul- 
iar to that region. The examination of specimens, however, show- 
ing what I considered intermediate phases of coloration from this 
same locality, led me to conclude that the form was not sufficiently 
distinct to receive a name, an impression’ which I now think was 
wholly erroneous. The reception of new material and a reconsid- 
eration of the question has convinced me that the form in question 
is quite distinct specifically from S. rvfus, from which it is separable 
by perfectly good and stable characters of external structure. As 
might be expected in a family where the females of totally different 
genera are often distinguishable only with difficulty, it is in the 
males that the differences are chiefly to be noted. The narrow 
outer tail-feathers are in the case of S. alleni sufficiently peculiar, 
however, to enable one to distinguish the females and even the 
young birds. 
The adult males are at once separable, not only by the bright 
green back, the green extending partially over the upper tail-coverts 
and contrasting sharply with the rufous of the tail, but even more 
readily by the very peculiar characters of the tail, as above indi- 
cated. These are perfectly constant in all the specimens I have 
seen, and have proved to be so also in all of the many individuals 
which have passed under Mr. Allen’s notice. 
In reference 'to the coloration of the S. alleni, I can state that the 
amount of variation in the adult males is very small. The back is 
always of a pure metallic green. Mr. Allen, whose authority is un- 
questionable, and who has had ample opportunity for ascertaining, 
writes me that the variation is extremely slight, and that a series of 
thirty males then before him showed no differences. On the other 
hand, I can assert with equal positiveness that the S, rufus never 
assumes this complete green phase of coloration. Of specimens 
