600 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4-1 h Ser. 



PLATE XXVIII 



Figure 1. Basalt in foreground; Merced cap on top of Spring 

 Hill, three-quarters of a mile west of Marin School, Petaluma Quad- 

 rangle. The basalt in turn rests upon Franciscan rocks. 



Figure 2. Tuffaceous Merced resting on basalt, corner Stanley 

 and Howard Sts., Petaluma. 



PLATE XXIX 



Figure 1. View looking southeast along the Hayward fault line 

 from highest point in road about one and one-half miles northwest 

 of Petaluma reservoir. Fault sag pond in the middle ground. Peta- 

 luma reservoir in distance. 



Figure 2. Flanks of Sonoma Mountain. Plateau determined by 

 hard, resistant tuff-breccia and lava flows overlain by softer shales 

 and sandstones of the Neohipparion beds of Lawler Ranch, a quarter 

 of a mile away. 



PLATE XXX 



Figure 1. Sonoma mountain top; a lava plateau. 



Figure 2. Looking southwest across the top of Sonoma Mountain. 



PLATE XXXI 



Figure 1. Petrified forest, five miles from Calistoga. View show- 

 ing "queen of the forest," a petrified redwood tree, which was once 

 almost entirely covered by volcanic tuff. 



Figure 2. A smaller, but more nearly perfect specimen, showing 

 the nature of occurrence in this interesting fossil forest. The tree in 

 figure 1, the tree here figured, and the other trees which have been 

 excavated all lie in the same general direction, tops toward the south- 

 west, and roots of the trees upturned toward the northeast, thus in- 

 dicating the direction from which the tuff-breccia mud flow which 

 engulfed these trees came. 



PLATE XXXII 



Figure 1. A view looking southwest toward the head of Tomales 

 Bay, Hog Island, center. A fault sag pond occurs in the middle 

 ground about twenty-five feet above sea level. 



Figure 2. View looking north from Dillon's Beach, showing a 

 small remnant of Pleistocene Terrace. 



PLATE XXXIII 



Figure 1. Unconformity between Tomales and Millerton forma- 

 tions, one and three-quarters miles northwest of Millerton. 



Figure 2. View showing unconformity between Millerton and To- 

 males Pleistocene formations, one and three-quarters miles northwest 

 of Millerton. Upper clays are horizontal. 



