80 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
plentiful. The same may be said of the White Mountain, or Sierra 
Blanca, which lies north from the Sacramento, and on which the Boreal 
is quite strongly marked. 
The Florida Mountains, southeast from Deming, show the Transition 
on their higher portions. 
The Potrillos or Colt Mountains, south from Afton on the Southern 
Pacific Railroad, and near the Mexican line, show only a touch of the 
Transition , and the same may be said of the Madelinas, west from Ma¬ 
son’s Ranch. The Dona Anas, north from Las Cruces, show likewise 
but a faint trace on their highest portions. 
The Sandia Mountains, east of Albuquerque, possess a well marked 
T'ansition , and likewise a well marked Boreal showing the Canadian and 
Hudsonian zones. 
Mexico. —The Transition extends throughout the Sierra Madre Moun¬ 
tains, in the States of Sonora, Chihuahua, and south into Durango about 
as far as latitude 24° or 25°. The Sierra Madre is a broad plateau from 
6000 to 9000 feet above the sea. The Boreal obtains on the crests and 
summits, a number of which rise to 10,000 feet and over. Though I 
have seen these mountains both from the east and from the west, I have 
never penetrated them. 
There are reported to exist in the northern portions of the Sierra 
Madre dense, unbroken coniferous forests of great extent. In' these 
Ursus abounds, and the streams contain mountain trout. Deer and 
mountain lion abound throughout the Sierra Madre. Some of the por¬ 
tions of the plateau are said by Schwatka to rise to 12,000 or even 
15,000 feet (La Sierra de los Ojitos). This, however, needs verification, 
as Schwatka’s information may have been unreliable. The writings of 
Lumholtz, Remington, and Schwatka may be read with interest in this 
connection. 
The Sonora Railway line passes through Transition in northern Sonora, 
just south of Nogales, Arizona. 
The only other Transition in Mexico known to me is that in the 
vicinity of the high volcanoes of the southeastern and southern por¬ 
tions of the plateau region. The highest of these are Orizaba or 
Citlaltepetl (about 18,000 ft.), Popocatepetl (17,800 ft.), Ixtaccihuatl 
(16,705 ft.), Toluca (about 16,000 ft.), Malintzi (15,840 ft.), Cofre de 
Perote (13,403 ft.), and El Pinal (11,220 ft.). On all of these peaks 
except the last the Boreal in all its zones is well marked above the Tran¬ 
sition. In the neighborhood of Ozumbaand Amecameca the Interoceanic 
Railway actually passes through firs, which indicate a touch of the Boreal 
even this low down, about 9000 feet or lower. This is just west of Popo- 
catapetl. There is probably, therefore, considerable of the Boreal on El 
Pinal as well, and also on the other peaks to be mentioned presently. In 
