EXPLANATION OF PLATE 2 



Fig. A. Irregular slab of black shale in Franciscan conglomerate, Mount 

 Diablo (one-quarter natural size). 



Fig. B. Franciscan conglomerate, Mount Diablo. Shows numerous subangu- 

 lar blocks of black shale, together with boulders of other types. Note the separa- 

 tion of the conglomerate into bands by ribs of sandstone. 



[44] 



