58 Nelson Description of New Birds from Mexico. 



I have to acknowledge again my indebtedness to Dr. C. Hart 

 Merriam, Chief of the Biological Survey, for his interest in the 

 work on Mexican Birds, and to Mr. Robert Ridgway, Curator, 

 and Dr. Chas. W. Richmond, Assistant Curator, of Birds in the 

 National Museum, for continued favors at their hands. 



All measurements are in millimeters. 



Heleodytes brunneicapillus obscurus subsp. nov. Mexican Cactus 



Wren. 



Type No. 142789, U. S. Nat. Mus., Biological Survey Coll. Ad. <?, Tula, 

 Hidalgo, Mexico, March 9, 1893. Collected by E. W. Nelson and E. A. 

 Goldman. 



Distribution. Tableland of Mexico. 



Description. Similar to H. brunneicapillus, from which it differs mainly 

 in its smaller size, darker crown, grayer back, more spotted chin, and the 

 obsolescence of white streaks on back. 



Average dimensions of H. brunneicapillus obscurus : 



Ad. tf (5 specimens): wing 85.8; tail 77.8; culmen 22.8; tarsus 27.6. 

 " $(5 " ): " 84.4; " 77.4; " 21.6; " 26.4. 



Averages of H. brunneicapillus (from southern California and 

 Arizona) : 



Ad. cp (5 specimens) : wing 90.4; tail 84.4; culmen 23.2; tarsus 29.2. 

 " ? (5 " ): " 85.2; " 81.8; " 21.6; " 27.2. 



The crown and nape on birds from the Mexican tablelands are sepia or 

 clove brown instead of burnt umber, as in those from southern California 

 and the southern border of the United States in general. This southern 

 form is dark grayish-brown on the back, lacking the paler or more rufous 

 shade of brunneicapillus proper. The white shaft lines of the dorsal 

 feathers are much reduced in width and are commonly broken up into 

 isolated spots. In viewing the dorsal surface of a series of the two forms 

 placed side by side the notable amount of streaking on typical brunnei 

 capillus contrasts strongly with the broken streaks and irregular white 

 spotting on the backs of obscurus. 



Specimens from northern Zacatecas show an approach to the northern 

 bird; those from the State of Nuevo Leon, in northeastern Mexico, are 

 intermediate in some characters, but may possibly represent a form pe 

 culiar to the Tamaulipan region. Nearly typical representatives of H. 

 brunneicapillus and H. b. obscurus are represented in the U. S. National 

 Museum series from southern New Mexico, and it is possible that both 

 may occur there, each having its range limited to certain altitudes. In 

 this case I should expect to find true brunneicapillus ranging below obscurus. 



The distribution of the two forms, so far as the material at hand allows 

 me to determine, is as follows: 



