246 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



cc. Bill much smaller (exposed culmen 22-24), less curved; spotting on V)reast 

 less distinct (obsolete in worn plumage). (Chatham Island, Galapagos 



Archipelago.) Nesomimus adamsi ( j). 249) 



66. Breast entirely unspotted. 



c. Bill larger (exposed culmen 19.7-28, usually much more than 20). 



(/. Rump distinctly rufescent. (Bindloe Island, Galapagos Archipelago. 



Nesomimus bindloei (p. 251) 



d(I. Rump not distinctly rufescent. 



e. Darker, dusky prevailing both on pileum and back; pale edgings on 



greater wing-coverts and tertials narrower or darker and less buffy. 



/. Bill longer (exposed culmen averaging 25.7 in male, 25.2 in female); 



flanks darker; sides of neck less 'extensively white. (Abingdon 



Island, Galapagos Archipelago) Nesomimus personatus (p. 252) 



ff. Bill shorter (exposed culmen averaging 22.6 in male, 21.9 in female); 



flanks paler; sides of neck more extensively white. 



g. Darker above; male averaging Aving 115.7, tail 111.2, exposed culmen 



23.3; female averaging wing 104.7, tail 102, exposed culmen 22.1. 



(James and Jervis islands — formerly Charles Island ? — Galapagos 



Archipelago.) Nesomimus melanotis (p. 253) 



gg. Paler above; male averaging wing 110.9, tail 107.2, exposed culmen 

 22.1; female averaging wing 102.5, tail 98, exposed culmen 19.7. 

 (Indefatigable and Seymour islands, Galapagos Archipelago.) 



Nesomimus dierythrus (p. 254) 



ee. Paler above, dusky not predominating on pileum or Ijack; pale edgings 



to greater wing-coverts and tertials broader or else paler and more buffy. 



/. Whitish tips to rectrices much broader. (Culpepper Island, Galapagos 



Archipelago.) Nesomimus hulli (p. 254) 



ff. Wliitish tips to rectrices much narrower. 



g. Wing longer (averaging 117.5 in male, 108 in female); whitish tips to 



rectrices smaller, divided mesially by a I^rown or dusky shaft-streak. 



(Tower Island, Galapagos Archipelago.) . . .Nesomimus bauri (p. 255) 



gg. Wing shorter (108-111 in male, 99-104 in female); whitish tips to 



rectrices larger, not divided by a brown or dusky shaft-streak. 



(Barrington and Wenman islands, Galapagos Archipelago.) 



Nesomimus barringtoni (p. 256) 



cc. Bill smaller (exposed culmen 19-20). (Albemarle and Narborough islands, 



Galapagos Archipelago) Nesominus parvulus (p. 256) 



I regret my inability to present a more satisf actor}^ ' ' ke}' ' ' to the 

 forms of this difficult group, but the material at my command is far 

 too meager for successful treatment of the subject. In the con- 

 struction of the ''key/' in framing the diagnoses, and in deciding 

 which are tenable forms I have been obliged to depend largely on 

 the papers of ISIessrs. Rothschild and Hartert and Snodgrass and 

 Heller, respectively, and use my best judgment in deciding questions 

 as to which the authorities cited are at variance. In such cases 

 my conclusion has favored the views of Messrs. Snodgrass and Heller 

 as being later and based on additional material. 



Messrs. Rothschild and Hartert consider all the forms character- 

 ized above, except N. frifasciatus, N. macdoiialdi, and N. adamsi, as 

 subspecies of N. melanotis, while Snodgrass and Heller recognize iV. 



