﻿NO. 7 SMITHSONIAN EXPLORATIONS, I926 5 1 



there is apparently fully proven by the fact that many of the bones 

 including the lower jaws and teeth had a considerable covering of 

 barnacles which can only live in salt or at least brackish water. The 

 fact that barnacles had attached themselves to the broken surfaces 

 is proof also that some of the l)ones had been broken before the 

 final covering. The presence of the barnacles also indicates that the 

 bones before their final covering had lain for some time just ofif 

 shore in shallow water. 



In connection with this story of the Venice mammoth, it seems 

 in order here to express to the officers of the Venice Company 

 appreciation for the courtesies extended to Dr. Gidley while engaged 

 in collecting the specimen and to commend them for their public- 

 spirited generosity in supplying all the material and labor needed for 

 the work as well as assuming for the Smithsonian Institution prac- 

 tically all incidental expenses in connection with it. 



COLLECTING MINERALS IN MEXICO 



Regarding the mineralogy and geology of Alexico comparatively 

 little is known. The country is rich in mineral wealth, producing 

 over 40 per cent of the world's silver, yet very few Mexican min- 

 eralogical collections have been made. This present exploration 

 was undertaken by Dr. F. W. Foshag of the Smithsonian Institution 

 in collal)oration with the Mineralogical Museum of Harvard Univer- 

 sity, for the purpose of collecting representative material from as many 

 of the districts as possible. Field-work was confined to that portion of 

 the plateau of Northern Mexico within the states of Chihuahua, 

 Coahuila, and Durango. 



The plateau region of Northern Mexico is characterized by a broad 

 high plain from which have been thrust upward numerous mono- 

 clinal or anticlinal ranges of mountains. The plains and valleys 

 between the ranges are clothed with grasses or scattered shrubs, 

 and the slopes carry a sparse covering of brush characteristic of 

 the Lower Sonoran life zone. This zone is characterized by a 

 number of yucca and cactus species, the creosote bush and, in nu- 

 merous places, the showy ocotillo. In a number of places the yuccas 

 form extensive open groves. Some of these desert plants are put 

 to economic uses ; maguey and sotol for fermented drinks, lechu- 

 guilla for fiber, candelilla as a source of vegetable wax, and guayule 

 for rubber. 



The ore deposits of the area visited may be considered a mineralogi- 

 cal unit. The most important are found in limestone of Cretaceous age 



