LIST OF ILU'sTRATTOm 



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



and the United States from tbe Eio Grande to the Pacific . Frontispiece 



Facing page. 

 II. Map showing differentiation tracts of the Mexican Boundary bine.. 2.°> 



III. Fig. 1. — Pinus ponderosa. 



Fig. 2. — West foot of San Luis Mountains 38 



IV. Fig. 1. — Juniperus californica. 



Fig. 2.— Salix taxifolia 42 



V. Fig. 1. — Yucca radiosa. 



Fig. 2. — Quercus gambelii 44 



VI. Fig. 1. — Populus fremontii. 



Fig. 2. — Across the Rio Grande River 48 



VII. Fig. 1. — Quercus agrifolia. 



Fig. 2. — Quercns hypoleuca 53 



VIII. Fig. 1. — Cerens giganteus. 



Fig. 2. — Cereus thurberi 65 



IX. Fig. 1. — Chilopsis linearis. 



Fig. 2. — Rio Grande opposite the First Monument 'is 



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. L— Monument No. 126, Elevated Central Tract. 



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



XIII. Fig. 1.— Tinajas Altas, Western Desert Tract. 



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



TEXT FIGURES. 



Fio. 1. — Diagram showing sections of Mexican Boundary bine 7 



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



3. — Tayassu angulatum. a, Right forefoot; 6, right hindfool 161 



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



view L63 



5. — Tayassu angulatum sonoriense. a, Skull, ventral view; i>, 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. </. Right hindfoot; b, right forefoot. 165 



9. — ( )il ocoi lens aniericaims. a, Skull; /», audital region 1 72 



10. — Tail of odocoilens couesi. a, Under surface; b, upper surface I7t; 



