VOL. XII, PP. 57-68 MARCH 24, 1898 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



DESCRIPTION OF NEW BIRDS FROM MEXICO, WITH 

 A REVISION OF THE GENUS DAGTYLORTYX. 



BY E. W. NELSON. 



Further study of the Mexican birds in the collection of the 

 Biological Survey, U. S. Department of Agriculture, reveals the 

 presence of several apparently undescribed species and sub 

 species. These new forms, like those already described from this 

 collection, were obtained by Mr. E. A. Goldman and myself dur 

 ing our explorations in Mexico for the Biological Survey. Our 

 work has covered a large portion of that country, and although 

 far from exhaustive has been conducted systematically, with the 

 desire to secure series of specimens from various altitudes and 

 areas with a view to determining the faunal relationships of the 

 different sections. Up to the time our work began, some six 

 years ago, ornithologists had given little consideration to the fact 

 that Mexico has various well-defined climatic areas aside from 

 the two main divisions of highland or temperate, and lowland or 

 tropical. The fact is that the highlands contain several definite 

 faunal areas, and the same is true of the lower tropical lands. 

 Faunal work in the United States has shown very clearly the 

 differentiation produced in wide ranging species by varied cli 

 matic conditions. In many instances this variation is so gradual 

 that the different extremes are given subspecific rank ; in others 

 the resultant forms are sufficiently segregated to be accepted as 

 full species. Precisely the same state of affairs exists in Mexico. 

 The material collected illustrates these conditions, and will aid 

 materially in working out the subordinate faunal areas of that 

 country. 



13 KIOT,. Soc. WASH., VOL. XII, 1898 (57) 



