550 BULLETIN 50, UNITED STATES NATIONAL MUSEUM 



tion of the feet resembles closely that of the buteonine genera Circaetus 

 and Spilornis, with which, on this account, Herpetotheres has often 

 been associated. The last-mentioned character is, however, appar- 

 ently purely adaptive (teleological), the feeding habits of these forms 

 being similar, snakes constituting an important, if not the principal, 

 part of their diet. Although so very different in general aspect from 

 the true falcons, this serpent-eating falcon is, when aroused or in 

 action, said to exhibit a spirit, irritability, and dash second to that of no 

 other bird of prey. 



Genus HERPETOTHERES Vieillot 



(?) Physeta Vieillot, Analyse, 1816, 24. (Tj^pe, by monotypy, Falco sufflator 



Gmelin {—F. cachinnans Linnaeus?).) 

 Physta (emendation) Gray, Hand-list, i, 1869, 31. 

 Herpetotheres Vieillot, Nouv. Diet. Hist. Nat., xviii, 1817, 317. (Type, by 



monotypy, Falco cachinnans Linnaeus.) 

 Herpethotheres (emendation) Vieillot, Tabl. Encycl. M6th., iii, 1823, 1247. 

 Herpethoteres (emendation) Lafresnaye, Rev. Zool., ii, 1839, 196. 

 Cachinna Fleming, Philos.-Zool., ii, 1822, 236. (Type, by monotypy, Falco 



cachinnans Linnaeus.) 

 Macagua Lesson, Traite d'Orn., 1831, 68. (Type, as designated by d'Orbigny, 



1839, Falco cachinnans Linnaeus.) 



Bill relatively short and deep (its depth at anterior edge of cere 

 nearly equal to chord of culmen), compressed, the culmen strongly 

 decurved from base, the tip of maxilla strongly but not acutely 

 uncinate, but not preceded by a tomial tooth, the tomium regularly 

 and strongly concave anteriorly and with a slight convexity near 

 middle portion; gonys strongly convex basally, strongly ascending 

 terminally, the tip of mandible truncated, the tomium sinuated (slight- 

 ly but distinctly concave anteriorly, convex posteriorly), but without 

 trace of subterminal notch; cere very short, the upper half of its 

 anterior outline nearly vertical, the lower portion (between one-fourth 

 and one-fifth) also nearly vertical, but much posterior to the upper 

 portion (nearly on vertical line with posterior edge of nostril). Nostril 

 relatively large, circular, close to anterior edge of cere, without obvious 

 central tubercle, its bony rim elevated superiorly and posteriorly. 

 Wing moderately long, its tip rounded (third to fifth primary, from 

 outside, longest, the first equal to or longer than ninth), the inner webs 

 of outer four distinctly sinuated, the sinuation disappearing on the 

 sixth. Tail a little shorter than wing, strongly rounded, the rectrices 

 (12) rather soft, tapering slightly toward their rounded tips. Tarsus 

 between one-fourth and one-fifth as long as wing, very stout, covered 

 nearly uniformly with small, rough, imbricated, more or less hexagonal 

 scales, the toes similarly scaled except distally, where the small scales 

 are replaced by broad transverse scutella (mostly confined to terminal 



