8 Nelson — New Birds from Western Mexico. 



rusty edgings to the neck and wing feathers of the latter bird being en. 

 tirely absent. Curiously enough, although the Tres Marias Islands are 

 only about one-fifth as far from the coast as Socorro Island, yet the Tres 

 Marias race is more distinct from B. borealis calurus than is socorroensis. 



Polyborus cheriway pallidus subsp. nov. Tres Marias Caracara. 



Type No. 156715, U. S. Nat. Mus., Biological Survey Coll., J 1 ad., Maria 

 Madre Island, Mexico, May 3, 1897. Collected by E. W. Nelson and 

 E. A. Goldman. 



Description. — General pattern of coloration as in P. cheriway, but much 

 paler or lighter brown. The darkest adult from the islands is somewhat 

 paler than the palest adult from the mainland in the considerable series 

 I have examined. The same proportionately paler colors prevail on im- 

 mature birds from the islands. The terminal black band on the tail of 

 the island bird averages narrower, and the other dark bars on the tail are 

 fainter. The light and dark markings on back at base of neck are in the 

 form of regular bars instead of being broken into a roughly wavy pattern 

 by the oval form of the black areas on the featliers, as in specimens of 

 cheriway from the mainland of Mexico. The wing, tail, and tarsus aver- 

 age shorter than in cheriway of the Mexican mainland, bill about the 

 same. Dimensions of type : wing, 370; tail, 198 ; culmen, 32; tarsus, 86- 



Averages of Polyborus cheriway (from mainland of Mexico). — r^ (4 speci- 

 mens) : wing, 392; tail, 208.7; culmen, 32.5; tarsus, 90.7. 9 (2 speci- 

 mens) : wing, 396.5; tail, 217.5; culmen, 33.5; tarsus, 89. 



Averages of P. cheriway pallidus. — tf (4 specimens): wing, 370.7; tail, 

 194; culmen, 32 ; tarsus, 86.5. $ (4 specimens) : wing, 386.5; tail, 205 ; 

 culmen, 32.7 ; tarsus, 88. 



A specimen from the mainland adjacent to the Tres Marias group ap- 

 proximates the island form, and a series might prove the birds from that 

 district to be intermediate. 



Trogon ambiguus goldmani subsp. nov. Goldman's Trogon. 



Type No. 156752, U. S. Nat, Mus., Biological Survey Coll., ad. cT, 

 Maria Madre Island, Mexico, May 10, L897. Collected by E. YV. Nelson 

 and E. A. Goldman. 



Description. — Males decidedly greener above than typical ambiguus, with 

 very little of the coppery iridescence characteristic of the latter. Females 

 and young differ still more, their backs being decidedly ashy and having 

 much paler rufous on middle tail feathers ; exposed parts of scapulars, 

 tertiaries, and wing coverts gray, mottled with fine, wavy, black lines 

 with slight indication of the brown which forms the main color of these 

 feathers in ambiguus proper; colors of lower parts decidedly paler. In 

 size the two forms differ but little. Dimensions of type : wing, 128; 

 tail, 148; culmen, 20; tarsus, 17. 



Averages of Trogon ambiguus. — (^ (4 specimens) : wing, 131 ; tail, 161.2; 

 culmen, 19.5; tarsus, 16.7. 9 (1 specimen) : wing, 127; tail, 170; cul- 

 men, 18.5 ; tarsus, 17. 



