MEXICAN BOUNDAEY LINE. 113 



110. Green carbonate of copper. — Sonora. 



111. Gray sulphuret and green carbonate of copper. — Copper mines of Presidio del Norte. 



112. Sulphuret of lead and silver, with crystals of sulphate of lead. — Santa Eosa. 



The specimens from Santa Rosa are from veins, and do not furnish any of the associated rock. 



The specimens of rock from the Leon mine are a semi-crystalline limestone of a mixed gray 

 and white color, with calcareous spar ; and a crystalline limestone colored brown by oxide of 

 iron. The other specimens from this locality are vein-stones or ores. 



In the vicinity of the mines of Corriletas, the limestone has undergone still farther meta- 

 morphism, and some specimens which occur in the same connexion, and apparently of this age, 

 assume a very crystalline character, and exhibit mica and some other minerals, which have 

 been segregated from the mass during the progress of metamorphism. 



The specimens of limestone from the Escandido mines include one of a yellowish white color 

 and crystalline texture, containing disseminated crystals of iron pyrites : this may be a vein- 

 stone. Another specimen is of very compact, bluish, granular limestone, with thin pressed 

 veins of spar, evidently having undergone some metamorphic action. This is labelled as coming 

 from the foot of the mountain adjoining the mines. Other specimens marked as from the same 

 locality contain large numbers of fossil shells, but in such a condition as to aiJbrd very unsatis- 

 factory means of determining their age. They present, however, many features like those of 

 tbe cretaceous limestones, and are probably beds of that formation, which have undergone 

 partial metamorphism. 



E. SPECIMENS COLLECTED ON THE ROUTE FROM THE PACIFIC COAST EASTWARD, INCLUDING 

 THE TERTIARY OF THE COAST AND THE METAMORPHIC ROCKS OF THE CORDILLERAS; THE 

 TERTIARY OF THE GREAT PLAIN EAST OF THE CORDILLERAS, AND THE METAMORPHIC ROCKS 

 OF THE ISOLATED MOUNTAINS IN THE GREAT PLAINS. 



IV. Specimens from the coast Tertiary belt, from the neighborhood of San Diego. 



1. Gray micaceous sandstone, with more or less of argillaceous matter, friable, or more or 

 less compact. 



2. Calcareous beds with shells, Turritella, Pectunculus, &c. 



3. A fine chalk-like, tufaceous deposit, occurring in isolated beds. 



4. Lignite, associated with clays and sands. 



V. Tertiary formations spreading over the plain east of the Cordilleras. 



1. Sands and marls with clays, all more or less calcareous ; represented as forming extensive 

 beds of considerable thickness, and cropping out in bluffs of several hundred feet high. 



2. Shells of Ostrea vesperfina, i'rom the beds of the preceding scries. 



3 . Calcareous tufa ; forming isolated masses or deposits. 



4. Gypsum — Selenite. This mineral occurs in the clays and marls of the formation. 



5. Common salt, forming on the borders of lakes from evaporation. The soil is more or less 

 permeated witli saline matter, which is carried downwards to the depressions in which occur the 

 small lakes having no outlets. 



15 M 



