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University of Texas Bulletin 



Cerro del Muleros near Ciudad Juarez at the same time, where the corre- 

 sponding beds consist entirely of sandstones. 



According to the observations of Haarmann and our palaeontological 

 studies the stratigraphical cross section of the Cerro del Macho presents 

 the following features : 



If really the beds with Inoceramus labiatus lie immediately on top of the 

 cephalopod beds, as the observations of J. G. Aguilera seem to indicate, 

 another deepening of the sea may have followed and the general rising 

 of the bottom of the ocean did not begin before the age of the lower Se- 

 nonian. 



ON THE RELATIONS BETWEEN THE FAUNA OF CERRO DEL 

 MACHO AND ISOCHRONOUS FAUNAS OF OTHER REGIONS 



OF THE EARTH 



The fauna of the upper Cenomanian of Cerro del Macho is too small 

 to be compared with others ; the most important fossil, Metoecoceras n. sp. 

 belongs to a group which has been found in the upper Cenomanian. Of 

 certain interest is the occurrence of Exogyra cfr. olisiponensis Sharpe be- 

 cause it indicates a faunistic similarity with the development of the Ceno- 

 manian along the border of the Mediterranean, a circumstance which to a 

 certain degree can be noted also in the fauna of other Cenomanian beds 

 of Mexico. 



