MAMMALS OP THE MEXICAN BOTJNDABY. 3 



biological work at the exact point where it had been left on my de- 

 parture for Fort Clark. My investigations along the whole line 

 were therefore continuous. 



The scientific work accomplished was of the nature of a biological 

 survey of the Mexican Boundary region, and agrees essentially with 

 the plan which I submitted to the Commission in January, 1892, be- 

 fore entering the field. Plants, vertebrate animals, mollusks, crus- 

 taceans, rocks, minerals, fossils, and a small amount of archeological 

 and miscellaneous material were embraced in the collections, which 

 were deposited in the United States National Museum. 



About 100 collecting stations were occupied during the course of 

 the survey, which extended over a period of nearly three years and 

 covered an extent of 700 miles of the Boundary. I had been sta- 

 tioned at three military posts on the Rio Grande in Texas, and 

 previously served for more than four years in the Territories of 

 Arizona and New Mexico. At each of these posts, as well as at each 

 of the collecting stations on the Boundary Line, an effort was made to 

 procure and preserve specimens of each vertebrate animal and 

 flowering plant that could be found, in order that the collections 

 might furnish indisputable evidence of the longitudinal dispersal 

 and variation of as many species as possible. 



It seemed important that the exceptional facilities afforded by this 

 survey for studying the degree and manner in which plants and 

 a-nimals vary along a parallel, and if possible the laws which govern 

 such variations, should be utilized as fully as possible. To this end 

 much time was devoted to gathering abundant material to show the 

 distribution and variation with locality, of the several species. The 

 longitudinal ranges of the species and subspecies (geographic races) 

 were carefully defined, and an approximately accurate knowledge of 

 the character and extent of the faunal and floral tracts crossed by the 

 Boundary Line was obtained. 



The collections were made by myself, with the occasional volun- 

 tary assistance of other members of the party and of Mr. Frank 

 X. Holzner, a collector employed at my request by the United 

 States National ' Museum and the American Museum of Natural 

 History in New York. About 30,000 specimens were forwarded to 

 the National Museum and distributed to specialists in the several 

 departments represented, for the purpose of detailed elaboration. A 

 report upon the Mollusca, with illustrations, by Dr. W. H. Dall and 

 Mr. Charles T. Simpson (genera Unio and Anodonta) , has been pub- 

 lished."^ Dr. Edwin C. E. Lord has published a Petrographic Eeport 



Report on the mollusks collected by the International Boundary Commission 

 pp. 333-379, pis. XXXI-XXXIII. (See also Nautilus, VI, April, 1893, p. 134, 

 and Proc. U. S. Nat Mus., XVII, 1895, pp. 1-6.) 



