64 BULLETIN 50, UNITED STATES NATIONAL MUSEUM 



inflatable air sacs ; postacetabular region of pelvis very broad ; hypocleid- 

 eum triangular; tarsometatarsus less than half as long as tibia. 



Bill relatively small, the culmen rounded (not ridged), the tomia 

 smooth; cere completely and densely feathered. Wing moderate, very 

 concave beneath, the longest primaries much longer than longest seconda- 

 ries; third or fourth primaries longest (fifth and third sometimes equal), 

 the first (outermost) intermediate between sixth and seventh, seventh and 

 eighth, or equal to eighth; primaries rigid, the outer ones much bowed 

 or incurved distally. Tail variable in form, usually decidedly shorter 

 than wing, the rectrices 16-20. Tarsus shorter than middle toe with claw 

 (except in Centrocercus), with at least the upper half densely feathered 

 (wholly feathered except in Bonasa and Tetrastes, the toes also feathered 

 in winter specimens of Lagopus), never spurred; middle toe, without 

 claw, shorter than tarsus ; lateral toes about equal, reaching to or slightly 

 beyond penultimate articulation of middle toe; hallux shorter (sometimes 

 much shorter) than basal phalanx of middle toe; claws relatively small, 

 slightly curved, rather blunt; toes usually with more or less distinct 

 lateral horny pectinations or comblike or fringelike processes (deciduous, 

 however, in summer) ; anterior toes connected at base by a web between 

 first phalanges. Head completely feathered except, sometimes, a naked 

 superciliary space. 



Of the characters that distinguish the Tetraonidae from other Galli- 

 formes some are variable in their development in different genera. The 

 naked superciliary space, for example, is inconspicuous in the campestrian 

 genera Tympanuchus, Pedioecetes, and Centrocercus but is conspicuously 

 developed in Lagopus, Dendragapus, and Canachites, especially the first, 

 and is brightly colored (red, orange, or yellow) during the breeding 

 season. Many genera possess, in the male, an inflatable air sac on the 

 side of the neck, this reaching its greatest development in Tympanuchus, 

 in which the sac when inflated is of nearly the size and color of a small 

 orange. The males of some genera also possess an ornamental erectile 

 tuft of feathers on each side of the neck, Tympanuchus having elongated, 

 rigid, narrow feathers inserted immediately above the air sacs, while 

 Bonasa has, in nearly the same position (the air sacs, however, being 

 absent) very broad, soft, nearly truncated feathers. The tail is extremely 

 variable in form and development. It is short and rounded in Lagopus 

 and Tympanuchus ; much longer and more or less fan-shaped in Bonasa, 

 Dendragapus, and Canachites; very short and graduated, with the middle 

 rectrices projecting considerably beyond the others, in Pedioecetes; and 

 considerably elongated, excessively graduated, with narrowly acuminate 

 rectrices in Cenfrocercus; while in the Palearctic genus Tetrao the tail 

 is forked, with the lateral rectrices curved or curled outward in the males. 

 The feathering of the tarsus extends nearly, if not quite, to the base of 

 the toes, except in Bonasa and Tetrastes, in which only about the upper 



