156 PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



brownish-white at the tip — the inner webs mostly white ; the termin;il 

 half with just discernible obscure bais of darker, these becoming gradu- 

 ally obsolete on the basal half; sometimes they are entirely obsolete for 

 the full length of the outer webs. Upper tail-coverts pure white, usually 

 immaculate, but sometimes barred; inner webs of primaries ashy, the 

 two or three outer ones more whitish, and sometimes barred with dusky. 

 In males, the middle of the breast, the tibiae, and crissum are usually 

 ochraceous, irregularly spotted with brownish-black. 



The darker-colored individuals in this stage are distinguishable from 

 the dark examples of the young of i^. sivahisoni only by the very much 

 stouter and longer tarsi. 



The adults vary but little. The white of the jugulum usually reaches 

 forward medially into the plumbeous of the throat, and in one ( $ ad., 

 Tehuantepec, Mexico; Sumichrast) it extends — iaterruptedly, however — 

 to the chin. Another male from the same locality has the scapulars 

 almost entirely rufous, with black shaft-streaks. The white of the lower 

 jjarts in the adult is of a pureness and continuity strikingly character- 

 istic of this species. 



A very young specimen from Paraguay has the tail more brownish, 

 more distinctly barred, and more ochraceous on the tip; the upper tail- 

 coverts are ochraceous, marked' with broad crescentic bars of blackish, 

 and the upper parts generally are variegated with ochraceous. 



The specimen collected by Dr. Merrill (No. 74,404) is an adult male in 

 fine plumage. It agrees strictly with Mexican examples of correspond- 

 ing sex and age. Dr. M. furnishes the following notes on this specimen : — 

 " Length, 19.20 ; extent, 47.40; wiug, 15.30; tail, 7.20. Feet and legs 

 yellow ; cere greenish yellow ; tip of bill dark, basal half bluish green ; 

 iris brown." 



Material examined. — United States National Museum, 13; Museum of 

 the Academy of Natural Sciences of Philadelphia, G; Museum of G. N. 

 Lawrence, Esq., 1; other specimens,* 4. Total number of specimens ex- 

 amined, 24. 



Measurements. 



This fine Hawk is a rather common resident on the extensive prairies 

 near the coast, especially about the sand ridges that are covered with 

 yucca and cactus. Its habits appear to be like those of the allied spe- 

 cies of Prairie Hawks. On the 2d of May, 1878, 1 found two nests, each 



* These are specimens collected on the Isthmus of Tehuantepec by Prof. F. Sumi- 

 chrast, and not entered in the Register of the National Museum. 



