The characteristics of the _Ampelidæ_ have already been presented in
the synopsis of allied families; chief among them, the short, broad,
depressed, and triangular bill with short gonys, the deeply cleft
mouth, the short tarsus, and the tendency to subdivision of its
lateral plates.
The South American genus, _Dulus_, probably forms the type of a
subfamily _Dulinæ_, characterized by the much arched gape of mouth,
the metatarsal scutellæ in two series, and the body streaked beneath,
as in young _Ampelis_. The two other subfamilies may be defined as
follows:—
Subfamilies.
COMMON CHARACTERS. Grape of mouth nearly straight. Metatarsal
scutellæ in three series. Body plain beneath.
Ampelinæ. Wings very long and much pointed, longer than the
short, even tail. First primary excessively rudimentary; the
outermost about the longest. Gape without bristles. Frontal
feathers extending forward beyond the nostrils.
Ptilogonatinæ. Horny appendages like red sealing-wax at end
of shaft of secondaries. Wings rounded, shorter than the
graduated tail. First primary nearly half the second. Gape well
bristled. Frontal feathers falling short of the nostrils. No
red horny appendage to wing-feathers.