The Ortyginæ of Bonaparte, or Odontophorinæ of other authors, are characterized as a group by the bidentation on either side of the edge of lower mandible, usually concealed in the closed mouth, and sometimes scarcely appreciable. The bill is short, and rather high at base; stouter and shorter than what is usually seen in Old World Partridges. The culmen is curved from the base; the tip of the bill broad, and overlapping the end of the lower mandible. The nasal groove is short. The tail is rather broad and long.
Synopsis of Genera found in the United States.
a. Head without crest.
Ortyx. Tail not much more than half the wings; outstretched feet reaching beyond the tail.
b. Head with a crest of a few long narrow, keel-shaped feathers.
Oreortyx. Crest-feathers very long, linear; tail scarcely more than half the wings; bill stout; claws blunt, the lateral not reaching the base of the middle claw. Toes of the outstretched foot reaching beyond the tail.
Lophortyx. Crest-feathers widening much terminally, and recurved at the ends. Tail nearly or quite as long as wings. Bill rather small. Claws acute, the lateral reaching to the base of middle one. Toes not reaching the tip of tail.
c. Crest soft, full, and tufted; composed of short, broad, depressed feathers.
Callipepla. Crest springing from the crown. Wing-coverts normal. Tail stiffened, nearly as long as the wings. Claws small, acute; outstretched feet not reaching the tip of tail.
Cyrtonyx. Crest occipital. Wing-coverts greatly developed. Tail very small and soft; half as long as the wings. Toes short; claws very long, blunted; outstretched feet reaching much beyond the tip of the tail.