2 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
now considered in detail, and a new key to the families presented, 
based upon more extended or special study. 
CHARACTERS OF THE TRACHEOPHONE MESOMYODI. 
Mesomyodian Passeres with (usually) a single pair of syringeal 
muscles, attached to the middle portion of the bronchial semirings, 
the syrinx tracheal, the lower end of the trachea consisting of thin, 
membraneous walls, about six of the usual semirings extremely thin, 
sometimes obsolete, the bronchi with both outer and inner tympani- 
form membranes, vibratory tracheal membranes being also present, 
the few muscles (usually only one pair) wholly lateral (being thus 
specially modified as a vocal organ;)* feet schizopelmous; tensor 
patagii brevis passerine. 
The Tracheophone Passeres are (excepting the small family Xeni- 
cide of New Zealand) a purely Neotropical group of birds, though, 
like many others, entirely absent from the Antillean Subregion. The 
various members bear a more or less close resemblance in external 
appearance as well as in habits to certain Oscinine families, though 
very distinct in their internal structure. Thus, among the Formica- 
riide (Antbirds), some forms closely resemble Shrikes (Laniide), 
others Wrens (Troglodytidz), and others again are strikingly similar 
to the Pittas (Pittide) > in form, though lacking entirely the beau- 
tiful coloration of the latter. The Dendrocolaptide and Furnariide 
embrace species which, so far as external appearance goes, might pass 
readily for Tree Creepers (Certhiide), Thrushes (Turdide), or even 
Larks (Alaudide); the smaller Pteroptochide are conspicuously 
wrenlike, while some of the Conopophagide are not very unlike 
Pipits (Motacillide). While they vary greatly in size, form, and 
« This peculiar structure of the organs of voice is thus described by its discoverer, 
Johannes Miiller (‘‘Ueber die bisher unbekannten typischen der Stimmorgane der 
Passerinen” (title incomplete), von J. Miller, Berlin, 1847): ‘‘The lower end of the 
trachea is flattened anteriorly and posteriorly; its walls are thin and membranous 
and contain extremely fine anterior and posterior half-rings, which are fastened at 
the sides by long elastic bands. The position of these half-rings is altered by the 
muscles attached to their sides. In all these birds the cartilaginous pessulus in the 
furcation of the trachea is wanting, and is replaced by a tendinous strap. The mem- 
brana tympaniformis passes over from one bronchus to the other. The bronchi con- 
tain half rings only. The membranous wall of the voice organ consists of two thin 
transparent membranes, of which the inner one is the mucous membrane.”’ 
By Professor Alfred Newton it is described (Dictionary of Birds, Part iv, p. 940) 
as follows: ‘‘The lower portion of the Trachea consists of thin membranaceous walls, 
about six of the rings being extremely thin or, as often happens, deficient. Both 
inner and outer tympaniform membranes exist in the Bronchi as well as some vibra- 
tory tracheal membranes. The few muscles, generally but one pair, are wholly 
lateral. The birds thus furnished are the TRacnzoPHoNas; their voice is very loud, 
and while it is being sounded the lower part of the throat swells out.’’ 
5 This, however, not an Oscinine family, but a member of the Oligomyodean or 
Haploophone group of Mesomyodi. 
