78 
GROUPING OF,THE STRATA. 
Thus the Sierra Monica appears to be made up of strata over 500 feet in 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 fossiliferous. Similar heds 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 ; hut 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 7, figure 1. 
