458 SYSTEMATIC SYNOPSIS. —PICARI^ — CYPSELIFOBMES. 
406. C. vaux^ (To Wm. S. Vaux, of Philadelphia.) Vaux's Swift. Similar; paler, the rump 
and upper tail-coverts lighter than the rest of the upper parts ; the throat whitish. Smaller ; 
length 4.50; wing the same; tail 1.67. Pacific Coast, U. S., and southward. Seems to be 
different from pelasgica, but perhaps the same as a S. Am. species. Nesting and eggs as in the 
: Humming-birds. 
Tenuirostral Picaries. These beau- 
tiful little creatures will be known on 
sight; and as the limits of this work 
preclude any adequate presentation of 
the subject, I prefer merely to touch 
upon it. 
The TrochilidcB, in all essential struc- 
tural characters, are nearest related to 
the Cypselid(E. These two groups have 
in fact been united by some in a super- 
family MacivcMres, in allusion to the 
length of the hand and its feathers, and 
tersely described as schizognathous In- 
sessores. The flying-apparatus is as in 
the swifts: a very deep-keeled sternum, 
for attachment of powerful pectoral mus- 
cles, a very short upperarm, but the 
distal segments of the fore limb length- 
ened, bearing a thin-bladed or even 
falcate wing; primaries 10, the 1st 
usually longest ; secondaries reduced to 6, and very short. Tail of 10 rectrices, but other^dse 
too variable to be characterized, presenting almost every peculiarity in size and shape as a 
whole, in size and shape of individual feathers, and often differing in form as well as color in 
the opposite sexes of the same species. Feet extremely small and weak, unfit for progression, 
formed exclusively for perching ; tarsi naked or feathered. Hind toe incumbent. Claws all 
large, sharp and curved. The bill exhibits the tenuirostral type in perfection, being long and 
extremely slender for its length ; it is usually straight, subulate or awl-shaped, or with lancet- 
shaped tip ; it is often decurved, sometimes recurved, and again bent almost at an angle ; in 
length it varies from less than the head to more than all the rest of the bird. The cutting 
edges of the mandibles are inflected : the rictus is devoid of bristles. The nostrils are linear, 
with a supercumbent scale or operculum, sometimes naked, oftener feathered. In size the 
Hummers average the least of all birds, the giants among them alone reaching a length of 6 or 
7 inches, the pygmies being under 3 inches ; the usual stature is 3 or 4 inches. In a few the 
coloration is plain, or even sombre; most have glittering iridescent tints — ''the most gor- 
geously brilliant metallic hues known among created things." The sexes are usually unlike 
in color. 
The chief anatomical peculiarity is the structure of the tongue, which somewhat resembles 
that of woodpeckers, in being protrusible or capable of being thrust far out of the beak by a 
muscular mechanism connected with the long horns of the hyoid or tongue-bone, which curve 
up around the back of the skull. The tongue is in effect a double-barrelled tube, supposed to 
be used to suck the sweets of flowers. The character of the sternum and wing-bones has been 
already mentioned. How perfectly the feet are fitted for grasping and perching may be inferred 
