PEELIMmABY DIAGNOSES OF ^¥AX MAMMALS FKOM THE 

 I\rEXICAX BOEDER OF THE UNITED STATES. 



By Edoar a. Mearns, M. D., 



Asfiislaiil Siiy<ieon, United States Army. 



This is tlie fourtli of a series of papers giving preliminary descrip- 

 tions of tlie new luamnials collected on the recent survey of tlie ^lexican 

 boundary.' 



In explanation of the meaning of the term Tract as used in these 

 papers, it should be stated that it lias been found necessary, for the 

 purposes of the report on the Mexican boundary collections, to divide 

 the boundary strip geographically as well as faunally. F((nii(illif, this 

 line across the continent gives a section through the several altudiual 

 zones from the Tropical to the Boreal, though almost all of it lies 

 within the Sonoran or Austral. GeographicaJUj, I have subdivided it 

 into (1) five principal tracts, and (2) others which are subsidiary — pro- 

 longations or irregular extensions of areas which are not fairly l>isected 

 by the Mexican boundary line; and to these we may as well add the 

 insular tracts at either extremity of the boundary parallel. These 

 tracts might well be styled "mammal variation tracts," for they are 

 based solely on the geographical variation of mammals, though geolo- 

 gists inform me that they mark very distinct geographic if not geologic 

 regions. Briefly, these geographical subdivisions of the boundary line 

 are as follows: 



A. Principal Tracts. 



1. Comtuiclie or Middle Texas Tract. 



2. Chihuahua or Eastern Desert Tract. 



3. Apache or Elevated Central Tract. 



4. Yiiiua or AVestern Desert Tract. 



5. San Diei^o or Pacific Coast Tract. 



B. Minor Tracts. 



1. Tanianlipan Tropical Tract (=^Rio Grande Einbayment). 



2. Sierra Madre Tract. 



0. Yaqni Basin Tract. 



4. Lower Californian Ti'oi)ical or Palm Tract. 



C. Insulat. Tracts. 



1. Padre Island Tract (Gulf of Mexico). 



2. Santa Barbara Island Tract (Pacific Ocean). 



'See Proc. U. S. Nat. Mus., XVII, pp. 129-130; XVIII, pp. 443-447; XVIII, No. 1081. 



[Advance sheets of this paper were published May 2.->, 1890. 



Note. — The advance sheets of this paper were issued as belonging to Vol. XVIII, 

 1895, but it was found impossible to include it in that volume, and hence its insertion 

 at this place. — Editor.] 



Proceedings U. S. National Museum, Vol. XIX— No. 1103. 



137 



