V °S 9 ^1 Allen, Origin and Distribution of N. A. Birds. 113 



single species of Psaltriparus extending southward to the higher 

 mountains of Guatemala, and another northward along the Pacific 

 coast to Washington. 



Certhia and Regulus belong to the northern hemisphere, ran- 

 ging over its northern half; Polioptila is tropical American, with 

 outlying species extending across the warm temperate. 



The cosmopolitan family Turdidag is represented by three 

 genera — Merula, Ttirdus and Saxicola — of wide dispersion, 

 and by two — Hesperocichla and Sialia — which may be con- 

 sidered as autocthonous ; the sixth genus, Afyiadestes,'is tropical 

 American, with a single species in the western United States. 



In concluding our review of the land birds, the results may be 

 summarized as follows: Total number of genera, 1S1 ; of these 

 55, or 30 per cent., are circumboreal or otherwise wide-ranging 

 Old World forms; 126 genera, 01-70 per cent., are American, 

 of which 35, or 28 per cent., are essentially tropical, leaving 91 

 genera, or about 50 per cent., as distinctively North American. 



Separating the Land Birds into the two categories of Passerine 

 and non-Passerine, we find that of the 75 non-Passerine genera, 

 36 per cent, are wide ranging Old World forms, leaving 64 per 

 cent, as American, of which latter 40 per cent, are tropical 

 American, leaving 30 per cent, of the whole as strictly North 

 American. Of the 106 genera of Passeres, only 25 per cent, are 

 circumboreal or otherwise widely distributed in the Old World, 

 leaving 75 per cent, as American, of which four fifths are strictly 

 North American, or 60 per cent, qf the Passerine genera. 



The total number of genera represented in North America (as 

 geographically restricted in the A. O. U. Check-List) of which 

 account is here taken, is 274; of these 129, or 44 per cent., are 

 either circumboreal or widely dispersed over the Old World, 

 leaving 145, or 56 per cent., as American. Of the latter 102 

 genera, or about 40 per cent of the whole, are distinctively North 

 American, and 43 genera, or about 12 percent, of the whole, may 

 be classed as tropical American. 



Of the distinctively North American genera 57 per cent, have 

 a general distribution over the continent, while of the remaining 

 43 per cent., 17 per cent, are eastern and 26 per cent, are western. 



In order to bring still more closely into relief the extent and 

 manner of the relationship of the North American avifauna to 



