Research, Inc.) excavated a series of sites in the north- 
ern Sierra de Tamaulipas, a number of which were in 
rock shelters along the Canyon Diablo (MacNeish, 1950). 
The northern Sierra de ‘Tamaulipas is about 20 to 60 
miles west of the Gulf of Mexico and from 60 to 100 
miles northwest of Tampico. The mountains themselves 
are an eastern spur of the Sierra Madre and are rela- 
tively steep, though they rise only to about 8000 feet 
above sea level. They are composed of Cretaceous lime- 
stone which was uplifted at the end of the Mesozoic era. 
Subsequent cutting by erosion has produced a series 
of steep-sided canyons, all of which eventually drain into 
the Soto la Marina River, which flows to the Gulf of 
Mexico. The climate is, generally speaking, dry, with 
rainfall (580 to 800 mm. per year) occurring mainly in 
the summer. The vegetation of the area is largely xero- 
phytic and includes mesquite (Prosopis juliflora DC.), 
epozote (Chenopodium ambrosioides \..), palmito (prob- 
ably a species of palm), yucca (Yucca spp.), zacaton 
(Muehlenbergia spp.), otate (Arundinaria spp.), prickly 
pear (Opuntia spp.), pita (ourcroea or A gave spp.), and 
tall grasses. 
Excavations of eight stratified sites (five of which were 
caves or rock shelters), as well as excavations or surface 
collections of about a hundred single-period archaeologi- 
cal assemblages in 1946, 1949 and 1954, revealed a long 
sequence of cultures. These have been termed (from late 
to early) as follows: Los Angeles Phase, La Salta Phase, 
Eslabones Phase, Laguna Phase, La Perra Phase, No- 
gales Phase, Lerma Phase, Almagre Phase, and Diablo 
Complex (MacNeish, 1950). The delineation of this cul- 
tural sequence and its significance will be dealt with in 
another publication. However, one site, La Perra Cave 
(I'm c 174), not only yielded stratified remains of three 
of the above-cited archaeological phases (Laguna, La 
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