332 



FALCONIBJi;. 



specimen first described. Tliis can only be accounted for by the 

 fact that Hawks have really no fixed laws of change in plumage, 

 and that it is impossible for any one to define exactly the regular 

 sequence of the variations. Jfo two birds are exactly alike ; for one 

 has the head more advanced, another the tail, and vice versa. Thus 

 the bird last noticed as donning his grey dress is veiy far advanced 

 as regards his body-plumage, but has not moulted his tail, whereas 

 those in the rufous dress are not so forward in their body-plumage, 

 but have already the tail of the adult (one being in the act of 

 moulting). 



Adult female. Slaty blue above and below; no trace of a nuchal 

 collar ; under surface narrowly but irregularly barred with white, 

 the under tail-coverts clear buff; under wing-coverts grey, thickly 

 barred with buffy white ; quills blackish, shaded with slaty grey 

 above, the secondaries entirely of this colour, the under surface 

 greyish white, with black bars and tips, less conspicuous on the 

 upper surface ; tail alternately crossed with two bands of black 

 above, with a broad intermediate band of ashy grey between, nar- 

 rowty tipped with ashy grey, barred with ochraceous buff and black 

 below, the bars very broad. Total length 17 inches, culmen 1-6, 

 wing ll'T, tail 7*5, tarsus 1-4. 



AdiiU male. A little smaller than the female. Total length 16 

 inches, culmen 1-55, wing 11, tail 7"5, tarsus 1-4. 



Hab. Central America, Guiana, Amazonia, BrazU, and Bolivia. 



a. c? ad. St. S. America. Dr. Gray [P.]. 



b. Juv. St. S. America. Dr. Gray [P.]. 



c. Var. St. S. America. Purchased. 



d. e. Juv. sk. S. America. 



f. Ad. St. Brazil. Purchased. 



g. Imm. st. S. America. Dr. Lidth de Jeude. 

 h. Ad. sk. Para. R. Graham, Esq. [P.]. 

 i. Ad. sk. Bahia. Dr. Wucherer [C.j. 



k. Ad. sk. Demerara. R. B. Sharpe, Esq. [P.]. 



I. Ad. sk. Trinidad. Purchased. 



m. Skeleton. Venezuela. Pm-chased. 



2. Leptodon megarhynchus. 



Regerhinus megarh-s-nchus, Des Murs, in Casteln. Voy. Zool., Ois. p. 9, 



pi. 1 (1855). 

 Cymindis megarhynchus, Grai/, Hand-l. B. i. p. 28 (1869) ; Scl. &■ 



Sah: Komend. p. 122 (1873). 



Nearly adidt. Above slaty blue, clearer on the head and darker on 

 the back ; wing-coverts brown, margined with deep ochre (evidently 

 remains of young plumage) ; quills brown, shaded externally with 

 ashy, the secondaries clearer brown with rufous-white tips ; under 

 surface of wings white at base, greyish white for the apical half, all 

 the quills barred above and below with dark brown ; lower back, 

 rump, and upper tail-coverts blackish brown, the latter barred near 

 the base and tipped with white ; tail alternately banded with black 

 and ashy brown, and tipped with white, the black bauds being much 

 the broadest, and between them and the ashy brown bands a faint 



