136 U. S. P K. R. EXP AND SURVEYS — ZOOLOGY GENERAL REPORT. 
In this species the metallic scales of the throat extend about as far back as in the Trochilus 
colubris. The tail feathers are all broad ; the outer one is rounded at the end and widens from 
the base ; the next succeeding feathers have the edges parallel at the base, and the tips rather 
acute. The innermost feather is a little shorter than the longest (by about .05 of an inch) ; 
the outermost about .15 shorter ; and the tail is thus moderately graduated and slightly 
emarginate. 
The general appearance of this bird is not unlike that of the common ruby-throated T. 
colubris, although the two are distinguishable by generic peculiarities. S. platycercus is the 
larger bird, although the bill, if anything, is a little smaller. The graduated tail, with the 
broad, rounded, almost oblanceolate outer feather, is, however, in strong contrast to the deeply 
forked tail, with the acutely tapering outer tail feather of T. colubris. 
A remarkable peculiarity in this species (shared by C. rufus) is seen in the outermost primary. 
This is narrower and more linear than in most of our other species, as well as straighter or less 
falcate. The terminal half inch is abruptly attenuated and linear, so as not to exceed .03 of an 
inch in width. 
The green of the throat in this species is purer and less mixed with golden than in the T. 
colubris. The throat has a violet purple reflection instead of a fiery copper red. The crissum 
and breast are of a purer white. All the tail feathers, except the innermost, (which is like the 
back,) have a cinnamon edging on the inner edge, except at the extreme tip ; this is seen on 
both webs of all, except the first, where it is confined to the inner. This border is very 
conspicuous on the outer edge of the fourth feather. 
I have no female of this species before me, but a specimen in the collection of the Philadelphia 
Academy, supposed to belong here, has no rufous on the tail. 
In comparing specimens in the Philadelphia Academy, as well as that from El Paso, with 
Gould's figure, this is seen to indicate a much larger bird, (nearly 4^ inches long,) with longer 
tail and broader feathers, the external more pointed. Whether this would indicate the fact of 
a confounding of two species I am unprepared to say. His figure of the female shows very 
distinctly a rufous margin to the tail feathers. 
For the determination of this species, now for the first time introduced into the fauna of the 
United States, I am indebted to Mr. John Gould, who identified it when examining the speci- 
mens of Humming Birds preserved in the Smithsonian Institution, 
List of specimens. 
Catal. 
No. 
Sex. 
Locality. 
When collected. 
Whence obtained. 
Original 
No. 
Collected by— 
6066 
3 
El Paso, Texas 
1851 
Maj. W. H. Emory 
J. H. Clark 
9007 
3 
Mexico 
Verreaux 
34873 
ATTH1S, Reich en bach. 
Atthis, Reichenbach, Cab. Journal fur Orn. Extraheft fur 1853, 1854. App. B. (named only.) 
I am not sure that the diagnosis given of this genus is that of its founder, but it will answer 
to separate a well marked form from the other North American species. It is most like Selas- 
phorus, and its species have usually been placed in this genus ; it differs, however, in the 
