LIST OF ILLITSTRATIOI^S. 



Plate I. Map showing stations along the land boundary between Mexico 



and the United States from the Rio Grande to the Pacific . Frontispiece 



Facing page. 

 II. Map showing differentiation tracts of the Mexican Boundary Line. . 23 



III. Fig. 1. — Pinus ponderosa. 



Fig. 2. — West foot of San Luis Mountains 3S 



IV. Fig. 1. — Juniperus californica. 



Fig. 2.— Salix taxifolia -12 



V. Fig. 1. — Yucca radiosa. 



Fig. 2. — Quercus gambelii - ^- 44 



VI. Fig. 1. — Populus fremontii. 



Fig. 2. — Across the Pio Grande River 48 



VII. Fig. 1. — Quercus agrifolia. 



Fig. 2. — Quercus hypoleuca 53 



VIII. Fig. 1. — Cereus giganteus. 



Fig. 2. — Cereus thurberi 65 



IX. Fig. 1. — Chilopsis linearis. 



Fig. 2. — Rio Grande opx^osite the First Monument 68 



X. Fig. 1. — Eastern edge of Animas Valley. 



Fig. 2.— San Pedro Valley '. 92 



XL Fig. 1. — View down Millers Canyon, Huachuca Mountains. 



Fig. 2. — Patagonia Mountains, showing Emory Oaks 102 



XII. Fig. 1.— Monument No. 126, Elevated Central Tract. 



Fig. 2. —Western part of Elevated Central Tract 107 



XIII. Fig. 1.— Tinajas Altas, Western De«ert Tract. 



Fig. 2.— Campo, California, Pacific Coast Tract 122 



TEXT FIGURES. 



Page. 



Fid. 1. — Diagram showing sections of Mexican Boundary Line 7 



2. — Distribution of trees on the west side of the Animas Mountains 92 



3.' — Tayassu angulatum. a, Right forefoot; h, right hindfoot 161 



4. — Tayassu angulatum sonoriense. a, Skull, lateral view; b, dorsal 



view 163 



5. — Tayassu angulatum sonoriense. a, Skull, ventral view; h, lower jaw, 



seen from above 164 



6. — Tayassu angulatum sonoriense. Skull, front view 165 



7. — Tayassu angulatum sonoriense. Inner surface of ear 165 



8. — Tayassu angulatum sonoriense. a, Right hindfoot; 6, right forefoot. 165 



9. — Odocoileus american\is. a, Skull ; b, audital region 1 72 



10. — Tail of odocoileus couesi. «, Under surface; 5, upper surface . . 176 



XI 



