332 MEMORIAS DE LA 'SOCIEDAD CIENTIFICA 
K 
Totolapa and is also found in the low land between Ajuchitlan and the 
limestone ridges. 
This breccia, as 1 have stated, Í class as Miocene. * but intimate 
that a division may be made between the breccia of the valley and that 
of the mountains referred to. * There are red shales associated with 
these breccias. In the valley I have indicated dykes. I am inclined to 
think that they are diorite in which case the assigned position of the 
diorite in the general section will not hold goods. * 
Lower Cretaceous.—The limestones of the San Gerónimo district 
are highly silicified and at the point where I have indicated a fault 
there is a silicious deposit in the form of a vein, having filled the cre- 
vice and which stands out prominently on the surface like a wall. 
[ have indicated the location of old mines in the limestones region. 
The limestone in places is replaced by ferruginous matter which car- 
ries copper and cinnabar. 
In one place in the Tinoco mountain (Miocene) there is a vein or 
fusime which is filled with ferruginous matter carryinga high percen- 
tage of copper ore. 
Cinnabar also occurs near the base of the Tinoco mountain in the 
red slates of the Miocene. Similar deposits of Cinnabar are found to 
the South east of Ajuchitlan. 
Section No. 2. Taken from Coyuca to Placeres. At Coyuca the lower 
Cretaceous linestones occur and are followed by red slates and breccia 
of the Miocene. There is apparently a fault as indicated in the section. 
Close to the margin of the Miocene breccia a granite conglomerate 
is encountered followed by the grey granites, which extend to and bey- 
ond the Oro river, where they are capped by the crystaline slates. 
1 The character of the breccia of the Balsas Valley is very similarto thatfound 
at Zacatecas and Guanajuato and from its appearance would appeat to be con- 
temporany- The localities are widely lid however but they may be det- 
ermined as identical. 
2 Should the referred to dykes prove o be diorite, it may be that the conglo- 
merate of the valley is Focene and the suggested division 6fthe conglomerates 
be correct. 
3 Iregret having lost my collection. The classificacion of the eruptive rocks as 
given in the general section I have taken from Prof. aguler, ofthe Geological 
Institute of Mexico. 
