78 GROUPING OF THE STRATA. 



Thus the Sierra Monica appears to be made up of strata over 500 feet iu thickness, which are 

 susceptible of division into two groups : 



1st. The hard sandstones, both red and yellow, which were observed along the Buenaventura 

 river, and which contain calcareous layers that are highly fossiliferpua. Similar beds are 

 found on the low hills near the Indian villages, four miles west of Santa Barbara. The thick- 

 ness of these over 300 feet. 



2d. The bituminous and argillitic beds — soft rocks — including foraminiferous beds, found 

 along shore near Arroyo Hondo and at La Purissima, and described under the report on the 

 valley of San Luis. Total thickness nearly 200 feet. 



Both of these groups are uplifted, contorted, and altered by the volcanic rocks which 

 elevated them. 



The Sierra Susanna was but hastily examined ; only the lower beds of the Monica hills 

 (group 1) were observed. It is probable that group 2 would be on its northern flank ; but this 

 district was not travelled over. 



An outline of the order of position ot the strata of Sierra Monica is given in plate 5, figure 

 2 ; also in plate 4, figure 5 ; and plate T, figure 1. 



