BT 1. 1. l.i in mi N i \i «>i ( OifPARAI i\ I. /""i '".i . 



The largest examples occur in tin- northern pari of i1 range, in 'I • 

 and Northeast Mexico, and from there southward the form gradually 

 merges into T, m. chloronotus. 



In freshly moulted birds the back i ;i little paler oli ve - g re en than 

 in true T. in. melancholicus, bu1 we cannot detect any differences in 

 tin- color of wings and tail of the two forms. 



THE FORMSOF PACHYRHAMPHUS POLYCHOPTERUS VIEILLOT) 

 AND PACHYRHAMPHUS MARGINATUS (LICHTENSTEIN). 



Having examined nearly all specimens of PochyrhamphtU poly- 

 chopterus and Pachyrhamphus marginatum available in this country, 

 we are able to throw some light on the geographical forms of these two 

 closely related species. 



Males of the paler forms of P. polychopterus superficially resemble 

 males of P. marginatus, but they are really quite distinct and readily 

 identifiable. The male of the /'. marginal us group differs from that 

 of the P. polychopterus group in having a broad white frontal band, 

 although some specimens of the polychopterus group, especially in the 

 paler forms, possess distinct white lores. 



The females of the two species are distinguishable at a glance. In 

 the P. polychopterus group the head of the female is of about the same 

 color as the back, or a little darker, while in the P. marginatus group 

 the head is always reddish brown, contrasting sharply with the olive- 

 green of the back. 



I. THE PACHYRHAMPHUS POLYCHOPTERUS GROUP. 



% 



There appears to be considerable confusion among ornithologists in 

 regard to the forms of Pachyrhamphus polychopterus, partly, no doubt, 

 owing to lack of material for comparison. 



The series of specimens at our disposal, arranged in accordance with 

 the geographical distribution of the species, not only shows very 

 plainly the existence of more forms than have hitherto been recognized, 

 but exhibits in a marked degree the great amount of individual varia- 

 tion in the plumage of the males of the darker forms. Berlepsch 

 (Nov. zool., 1908, 15, p. 140) -and Cherrie (Mus. Brooklyn inst. Sci. 

 bull., 1916, 2, p. 252), both have called attention to this variation. 



The females also show much individual variation. The color of the 



