No. I.] NORTH AMERICAN PASSERES. 103 
Oscines in this place, deferring all such questions to the closing 
arguments of this paper, in the “Conclusions,” where they 
more properly belong, and now at once proceed to the consid- 
eration of the skeleton in our American clamatorial birds, of 
which there are some thirty-six species and sub-species in our 
United States avifauna. 
By referring to the scheme of the families as given at the 
commencement of this paper, it will be seen that the clamatorial 
family, the Zyrannide@, about to be considered, occupies the first 
position in the list, which there means that it is of the lower, 
indeed lowest, group of passerine birds, so far as we are enabled 
to judge from their structure. 
Coues in characterizing this family has said that it is peculiar 
to America, and is “one of the most extensive and character- 
istic groups of its grade in the New World, the Zanagride and 
Trochilide alone approaching it in these respects. There are 
over 400 current species, distributed among about 100 genera 
and sub-genera. As well as I can judge at present, at least 
two-thirds of the species are valid, or very strongly marked 
geographical races, the remainder being about equally divided 
between slight varieties and mere synonyms. Only a small frag- 
ment of the family is represented within our limits, giving but 
a vague idea of the numerous and singularly diversified forms 
abounding in tropical America. Some of these grade so closely 
toward other families, that a strict definition of the 7yraunide 
becomes extremely difficult; and I am not prepared to offer 
a satisfactory diagnosis of the whole group” (Key, 2d ed., p. 
428). For the manner in which the family has been classified 
by our avian systematists, the reader is once more referred to 
the A. O. U. Check-List. The material at present at my hand, 
some of which I am greatly indebted to Mr. H. K. Coale of 
Chicago for, by which I hope to pass in review the skeletology 
of the Zyrannide, comes mainly from the genera Tyrannus, 
Mytarchus, Sayortus (all three species), Coxtopus, and Empidonax. 
Figures 18 to 21 inclusive, of the Plates, illustrate skulls and 
other bones of these birds; and when speaking above of the 
craniology of Lanzus, I dwelt to some extent upon certain 
features which characterize the skull of Myzarchus. As a rule 
in these Zyrannide, the brain-case is comparatively small and 
the sides and vault of the cranium rounded. Relatively, the 
