334 MEMORIAS DE LA SOCIEDAD CIENTIFICA 

synclinal formed ofthe Escamela limestone. The Eocene limestone con- 
glomerate is found within the synelinal basin. The character of this 
conglomerate is identical to that encountered at Tonelapa del Rio (see 
San Miguel) Beyond Mal Paso the Olive slates reap- 
pear and extend to the vicinity of Huetamo. 
The Cerro del Fresno just east of Huetamo is capped by the massive 

section Iguala 
limestones of the Escamela group, which rest upon the upturned adges 
of the slate. 
In the vicinity of San Pedro an antielinical occurs in the slates. The 
coal seams indicated occur somewhat north of the line of section. 
They are associated with slates and fine grey and blueish colored 
sandstone. The coal is of no commercial value, ocurring in exceed- 
ingly narrow, seams and often times merely beds of sandstone with 
carbonized plant remains. l am inclined to think that the olive slates 
are posterior to the Coyuca limestone, on account of the fine limestone 
conglomerates encountered in places near the Fresno mountain and 
interstratified with the slates, giving evidence of a preexisting limesto- 
ne and also of a marked hiatus. 
Section No. 4.—Is taken from the Balsas river at Santiago some 16 
kilometers below Zirándaro (about 480 K. from Mexico City by R. R. 
survey) to Espíritu Santo. The length of the section is about 15 kilo- 
meters. Close to the river the granite is covered by alluvial soil. Limes- 
tone occurs in basins in the granite in various places. To which group 
this limestone belongs, 1 am unable to state at present. 
The granite is succeeded by hornblendic gneiss toward Espíritu 
Santo. 
Section No. 5.—Is a view of the Pliocene breccia, which occurs in 
great force along the lower Balsas river and to the westward of Zirán- 
daro. . 
In the particular case represented, the breccia rests upon the pyro- 
xene andecites of redish color, but it is also found capping the grani- 
tes to the east of the point where the view is taken. The breccia is 
compound of the andecite porphyry, exclusively, as far as 1 have seen. 
The breccia forms a prominent topographical feature throughout 
his section of country. 
