275 



repose on a bed of clay, under which is again 

 found basalt. In general that of Regla is super- 

 posed on the porphyry of Real del Monte, while 

 a floetz limestone serves as a basis to the basalt 

 of Totonilco. The whole of this basaltic region 

 is two thousand metres above the level of the 

 ocean. 



r 2 



