598 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



have enlarged and modified one of the fault-sag ponds along 

 this rift by damming its southeast side. This rift, like the 

 San Andreas Rift, lends itself particularly well for reservoir 

 sites, as it crosses the normal courses of the streams on the 

 mountain slopes and makes their diversion an easy and 

 natural one along its trend. At the same time the city of 

 Petaluma should provide an adequate secondary reservoir 

 as insurance against earthquake movement along this zone of 

 recent seismic activities. 



Explanation of Plates 



PLATE XIX 



The sketch model of the Central Coast Ranges of California repre- 

 sented upon this plate is thought to be correct to the extent of giv- 

 ing a reasonably accurate impression of the general features of the 

 central coast region of California. No reliable topographic maps 

 exist for the major portion of the area shown. The exact elevation 

 of the mountains of the extreme northern portion is known in rela- 

 tively few instances; elevations south of the Golden Gate are fairly 

 accurate. From photograph by Professor R. S. Holway, Geography 

 Department, Univ. of Calif. 



PLATE XX 



Photograph of sketch model and index map of San Francisco Bay 

 Region and the Russian River, prepared under the direction of Pro- 

 fessor R. S. Holway, Geography Department, Univ. of California. 

 This picture was kindly loaned by Professor Holway. 



PLATE XXI 



Figure 1. View from Tomales-Dillon's Beach road about two miles 

 west of Tomales, looking northwest, showing Merced sandstone in 

 the foreground and marine plain on the sky-line. Elevation about 

 500 feet. 



Figure 2. View from Tomales-Dillon's Beach road about two miles 

 west of Tomales looking west, showing Tomales Point and the en- 

 trance to Tomales Bay. The small hill, Tom's Point, surrounded by 

 water near the extreme left of the picture is composed of Pleistocene 

 beds which dip to the east about ten degrees. 



PLATE XXII 



Figure 1. View from a hill about two miles west of Tomales 

 showing east end of tilted marine plain, looking northeast toward 

 Santa Rosa. This plain is cut in Merced Pliocene rocks. Franciscan 

 rocks are exposed in deeper stream canyons which are incised in this 

 plain. 



Figure 2. View from Tomales-Dillon's Beach road looking west, 

 about one and three-quarter miles west of Tomales showing coarse 

 conglomeratic Merced sandstone dipping about 10°-15° to the north- 

 east. 



