Mr. Dall states that the eggs are usually four in number, of a greenish-white color, and were usually all laid by the first of May. An egg of this bird, obtained by Mr. Dall at Nulato, April 27, 1858, measures 2.28 inches in length and 1.90 in breadth. It is of a rounded-oval shape, and is of a uniform dead-white color, with hardly a tinge of green. Another, obtained by Mr. Charles Pease near the head-waters of the Unalakleet River, measures 2.32 by 1.80 inches, and the ground-color is more distinctly greenish-white. A few small spots of a bronze-brown are scattered in isolated marking irregularly over the egg. Lieutenant Bendire writes that he has found the eggs of this Hawk in Montana; that their number in a set is usually two, and an unspotted white. GENUS ASTURINA, VIEILLOT. _Asturina_, VIEILL. 1816. (Type, _Falco nitidus_, LATHAM.) GEN. CHAR. Somewhat similar to _Astur_, but of much heavier and more robust build; tarsi longer and stouter, tail shorter and less rounded, wings longer, etc. Bill more elongated than in _Astur_, the cere longer, and the festoon on the commissure more developed; nostril oval, horizontal. Wings rather short, but less concave beneath than in _Astur_; third to fourth quill longest; first shorter than eighth or ninth; four outer quills with their inner webs sinuated. Tail considerably shorter than the wing, slightly emarginated, the lateral pair of feathers longest. Feet large and robust, when outstretched reaching almost to the end of the tail; tarsi very robust compared to the toes, about one and a half times as long as the middle toe, the frontal and posterior rows of transverse scutellæ very distinct and regular; outer toe longer than inner; claws strong, well curved, but not very acute. Sexes alike in color; old and young plumages very different. [Illustration: =34002=, ♀. ½ =34002=, ♀. ¼ =34002=, ♀. ½ _Asturina plagiata._] This genus is peculiar to tropical America, and contains but a single species, the _A. nitida_, with its two climatic races, _nitida_ of South America and _plagiata_ of Middle America. The species of _Rupornis_, Kaup (_R. magnirostris_ and _R. leucorrhoa_), have been associated with the species of the present genus, but they are very distinct. The genera (or, more properly, subgenera) most nearly related to _Asturina_ are _Leucoptrinis_, Kaup, of tropical America, and _Kaupifalco_, Bonap., of Western Africa. The former differs mainly in more or less rounded, instead of emarginated, tail, and in having the old and young plumages similar; the latter in having the posterior face of the tarsus without a well-defined row of transverse scutellæ. Species and Races.