_Nauclerus_, VIG. 1825. (Type, _Falco furcatus_, LINN.; _F. forficatus_, LINN.) _Elanoides_, GRAY, 1848. (Same type.) GEN. CHAR. Form swallow-like, the tail excessively lengthened and forked, and the wings extremely long. Bill rather small, and narrow; commissure faintly sinuated; upper outline of the lower mandible very convex, the depth of the mandible at the base being only about half that through the middle; gonys drooping terminally, nearly straight. Side of the head densely feathered close up to the eyelids. Nostril ovoid, obliquely vertical. Feet small, but robust; tarsus about equal to middle toe, covered with large, very irregular scales; toes with transverse scutellæ to their base; claws short, but strongly curved; grooved beneath, their edges sharp. Second or third quill longest; first shorter than, equal to, or longer than, the fourth; two outer primaries with inner webs sinuated. Tail with the outer pair of feathers more than twice as long as the middle pair. The genus contains but a single species, the N. FORFICATUS, which is peculiarly American, belonging to the tropical and subtropical portions on both sides of the equator. The species is noted for the elegance of its form and the beauty of its plumage, as well as for the unsurpassed easy gracefulness of its flight. It has no near relatives in the Old World, though the widely distributed genus _Milvus_ represents it in some respects, while the singular genus _Chelictinia_, of Africa, resembles it more closely, but is much more intimately related to _Ictinia_ and _Elanus_. [Illustration: =52994=, ♂. ½ =52994=, ♂. ½ =52994=, ♂. ¼ ¼ _Nauclerus forficatus._] Species. =N. forficatus.= Head, neck, entire lower surface, and band across the rump, immaculate snowy-white; upper surface plain polished blackish, with varying lights of dark purplish-bronze (on the back and shoulders) and bluish-slaty, with a green reflection in some lights. _Young_, with dusky shaft-streaks on the head and neck, and the feathers of the upper parts margined with white. Wing, 15.40–17.70; tail, 12.50–14.50; culmen, .70–.80; tarsus, 1.00–1.30; middle toe, 1.15–1.20. _Hab._ The whole of tropical, subtropical, and warm-temperate America. Accidental in England. Nauclerus forficatus, (LINN.) RIDGWAY. SWALLOW-TAILED HAWK; FORK-TAILED KITE.