[Bead before the Texas Academy of Science , June 15, 1897.'] 
ON THE BIOGEOGRAPHY OF MEXICO AND THE SOUTH- 
WESTERN UNITED STATES. 
II. 
BY C. H. TYLER TOWNSEND. 
In these Transactions , I, pp. 71-96, the writer published a paper on 
the biogeography of Mexico, Texas, Hew Mexico, and Arizona,, special ref- 
erence being made to the limits of the life areas. Since the date of com- 
pletion of that paper, Sept. 23, 1895, the writer has had the opportunity 
of visiting additional territory and making further observations in this 
region, particularly in Mexico. The results of this work are presented 
here as supplementary to the first paper. 
MEXICO. 
TAMAULIPAS AHD HUE VO LEOH.— In the latter part of Sep- 
tember and first part of October, 1895, the trip was made from Mata- 
moros, in Tamaulipas, to Monterey, in Hnevo Leon, going by rail as far 
as San Miguel, about 80 miles, and performing the rest of the distance, 
some 130 miles, by stage. The route traversed was as follows: Mata- 
moros, Ramirez, Reynosa, San Miguel (end of railway), San Francisco, 
Camargo, Mier, Las Chicharrones, General Trevino, Cerralvo, Papagallos, 
Doctor Gonzales, Marin, and Monterey. The region passed through is 
an extremely interesting one, being on the northern dilute confines of 
the Neotropical, distinctly Lower Sonoran in the preponderance of its 
forms, hut with a suggestion of the Neotropical here and there. An as- 
cent of something less than 2000 feet is reached at Monterey, the ascent 
being’ very gradual all the way, except in crossing a foot-hill range beyond 
Cerralvo. The neighborhood of the Rio Grande is kept all the way from 
Matamoros to Mier, when the stage road strikes to the south into the 
interior. From Matamoros to Mier, and south as far as Cerralvo, the 
vegetation is characteristic of the Lower Sonoran — mesquite trees ( Pro - 
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