10 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 
KEY TO THE GENERA OF FORMICARIIDH.® 
a. Planta tarsi compressed and more or less sharply ridged behind, consisting of two 
parallel rows of scutella or undivided lamina, whose line of contact forms a median 
posterior ridge. (Formicariinz.) 
b. Second phalanx of middle toe entirely free from outer toe; acrotarsium more or 
less distinctly scutellate (at least on inner side). 
c. Nostril oval or roundish, pierced directly into the completely ossified nasal 
fossee, without trace of operculum or adjacent membrane. (Thamnophilex.) 
d. Bill more swollen and relatively shorter and broader, its depth at frontal 
antiz much more than one-third the length of the commissure. 
e. Tail shorter than wing; tarsus shorter than conlmissure; plumage nar- 
rowly barred, above and below. .....--------..-- Cymbilaimus (p. 18). 
ee. Tail much longer than wing; tarsus longer than commissure; plumage 
spotted above, nearly unicolored (not barred) below. 
Hypeedaleus (extralimital).6 
dd. Bill less swollen, relatively longer and narrower, or else more compressed, 
its depth at frontal antize much less than one-third the length of 
commissure. 
e. Tail much longer than wing. 
f. Bill relatively longer (exposed culmen longer than middle toe without 
claw), much stronger, less tapering terminally, the unguis larger and 
more abruptly hooked; upper parts transversely barred; very large 
(total length 300 mm. or more) ..........-...-- Batara (extralimital).¢ 
jf. Bill relatively smaller (exposed culmen not longer than middle toe 
without claw), much weaker, more tapering terminally, the unguis 
smaller and weaker; upper parts spotted (not barred) or immaculate; 
smaller (total length not more than 250 mm.). 
@In order to show more clearly the relationship of the various groups, a number of 
extralimital (South American) genera are included. My efforts have been handi- 
capped by the lack of many species desired for comparison, among which are the 
types of the following generic or subgeneric names: 
Neoctantes Sclater. (Type, Xenops niger Pelzeln.) 
Myrmophila Cabanis and Heine. (Type, Formicivora brevicauda Swainson.) 
Terenura Cabanis and Heine. (Type, Mytothera maculata Maximilian.) 
Psilorhamphus Sclater. (Type, Leptorhynchus guttatus Ménétriés.) 
Microbates Sclater and Salvin. (Type, Rhamphocxnus collaris Pelzeln.) 
Myrmochanes Allen. (Type, M. hypoleucus Allen.) 
Rhopornis Richmond. (Type, Myiothera ardesiaca Maximilian.) 
Sclateria Oberholser. (Type, Sitta naevia Gmelin.) See footnote on p. 16. 
Percnostola Cabanis and Heine. (Type, Lanius funebris Lichtenstein.) 
Thamnocharis Sclater. (Type, Grallaria dignissima Sclater and Salvin.) 
Grallaria Vieillot. (Type, Formicarius varius Boddaert.) 
The genus Terenura, although represented in the geographic field covered by this 
work, is necessarily omitted from the ‘‘key,’’ because I have not been able to examine 
a specimen of any species. (See p. 83.) 
+ Hypoedaleus Cabanis and Heine, Mus. Hein., ii, Aug., 1859, 18. Type, Thamno- 
philus guttatus Vieillot. (Southeastern Brazil; monotypic.) 
¢ Batara Lesson, Traité d’Orn., 1831, 347. Type, Vanga striata Quoy and Gaimard= 
Thamnophilus cinereus Vieillot—Thamnarchus Cabanis and Heine, Mus. Hein., ii, 
1859, 19. Type, Thamnophilus cinereus Vieillot. (Batara rejected on grounds of 
purism.) (Southeastern Brazil; monotypic.) 
