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



the Easterly dip of these beds is but one or two degrees. In 

 and around Freestone low dips were prevalent and apparently 

 the Merced strata are but slightly undulatory, as the Fran- 

 ciscan base is seen in the bottom of Salmon Creek near Free- 

 stone and again as a noteworthy mass of serpentine about 3 

 miles east of Freestone. As the Merced sediments are traced 

 southward on the west side of Santa Rosa and Petaluma 

 valleys, similar conditions were found as respects their gen- 

 eral attitude. Locally, however, dips as high as 10° to 15° 

 were recorded around Tomales, Bodega village, and near the 

 Cinnabar School, two miles north of Petaluma, where a 

 westerly dip is recorded. Apparently some minor folding 

 or faulting has occurred in a few places, but the writer 

 questions the synclinal character of Santa Rosa Valley. The 

 hills bordering the Santa Rosa Valley on the east, two to 

 four miles north of Santa Rosa, are composed of tuff and 

 interbedded sandstones with dips at certain localities as high 

 as 40° to the east. The Hayward fault is probably expressed 

 by the sharp separation of the main valley and the eastern 

 bordering hills, and is approximately parallel to the state 

 highway. No other fault characters were recognized in this 

 vicinity, however. Santa Rosa Valley seems to be due 

 chiefly to erosion in soft, nearly horizontal, Merced strata, 

 but complicated by minor folding and faulting. The best 

 known Merced locality is at Wilson's Ranch, a half mile east 

 of Russian River, where a very characteristic, well-preserved 

 fauna occurs. At this place the Merced is composed of hard, 

 gray, conglomeratic sandstone which has an easterly dip of 

 1° to 2°, and a soft, tuffaceous, yellow sandstone with minor 

 strata of tuff, interbedded. This yellow sandstone with 

 minor tuff members, is the commonest lithologic character 

 of the group throughout this field. 



The following fauna was obtained at Wilson's Ranch: 



Bathytoma carpenteriana fernandoana Arnold. 



Crepidula adunca Sowerby 



Drillia mercedensis Martin 



Nassa californiana Conrad 



Nassa moraniana Sowerby 



Natica consors Dall 



Olivella biplicata Sowerby 



