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390 BULLETIN 133, UNITED STATES NATIONAL MUSEUM
El precedente I take to refer to the preceding species, the yapu
{Ostinops decumanus) that has a light colored bill which contro-
verts Vieillot's statement that in soUtarius the bill is black.
Though formerly placed in the genus Amhlycercus the species
soUtarius is apparently a cacique. Amhlycercus holosericeus has a
strongly operculate nostril, no crest, and the eighth primary shorter
than the second, while ArchipJanus solitarms has the nostril nonoperculate,
the eighth primary longer than the third, the wing
longer, and a decumbent crest.
The differences between soUtarius and holosenceus have been dis-
cussed recently by Miller,^^ but Avithout making a change in their
current status. Todd^^ includes soUtarius in the genus Archiplmius
Cabanis, a group segregated by Miller in the paper cited
above. I had recognized also that soUtatius must be removed from
Amhlycercus, and concur in Todd's allocation of it in the genus
ArcMplanus. The bill in soUtan^is is broader at the tip than in
Archiplanus aJMrostri.s, type of Cabanis's genus, but the form of
the decumbent crest and of nostril, wing, and tail are closely similar
in the two birds and indiqate clearly their relationship. Todd is
somewhat confused in the structural characters assigned to holosericeus
and soUtarius, since it is hxAosei^iceus that has nostrils linear and
overhung by a membrance, not soUtarius as stated.
The species here discussed was found at only three localities:
Las Palmas, Chaco, July 23 (adult male taken) and 26; Riacho
Pilaga, Formosa, August 14 (adult male) ; and Kilometer 200, west
of Puerto Pinasco, Paraguay, where three were seen September 25.
The birds were encountered in heavy brush where attention was
called to them by their harsh notes, quay quay. They were alert and
active and peered out with tail thrown over the back, but at any
alarm disappeared in dense scrub and were lost to view. The light
colored bill showed prominently, even when they were seen in tilting
flight across openings in the thickets. Like Archiplanus chrysopterus
when feeding they poked and pried at leaves or loose bark
with open bill. On examining them I was struck by the utility of a
development noted frequently in some orioles, Amhlyrhaniphus,
other Icterids, and in the genus Sturnus among other birds, where
the angle of the lower jaw (the processus angularls posterior) is
prolonged behind the articulation as a slender bar. Contraction of
the bands of muscle thfit pass from this bar of bone to the side of
the skull force the tip of the lower jaw away from the upper, with
the articulation of the lower jaw with the quadrate acting as a ful-
crum. The bill is thrust into or under bits of bark, a rolled leaf,
8«Auk. July, 1924. pp. 463-4G7 (received in WashinRton July 5, 1024).
8'Proc. Biol. Soc. Washin.gton, vol. 37, July S, 1024. p. 114.