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CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



stone with dip of 15° W. and strike of N. 20° E. The 

 sandstone forms the limb of a small syncline which is ap- 

 parently truncated by a Pleistocene marine plain. Here, as 

 around Freestone, several of the canyon bottoms expose 

 Franciscan rocks. Most of the hills between Bodega and 

 Valley Ford are capped or composed of Merced sandstones. 

 At Valley Ford the rocks of this group are horizontal and 

 the lowermost member consists of a coarse-grained, conglom- 

 eratic sandstone or finely-grained conglomerate whose peb- 

 bles are nearly all red chert. This resistant sandstone has 

 given rise to the picturesque little buttes seen about the vil- 

 lage of Valley Ford. Similar conditions occur around 

 Tomales where the hills are capped by Merced sandstone laid 

 down upon an old erosion surface cut in Franciscan rocks. 

 About two miles west of Tomales, on the Tomales-Dillon's 

 Beach Road, the Merced outcrops boldly as a massive coarse- 

 grained conglomeratic sandstone which has a local dip to 

 the east of 15° with strike of N. 35° W. The sandstone is 

 truncated near this point by a marine plain at an elevation 

 of about 400 feet. (See plates XXI and XXII.) In the 

 sea cliff at Dillon's Beach, Franciscan sandstone with lignite 

 is well exposed so that it is evident the Merced in this vi- 

 cinity rests upon a Franciscan base at no very great depth. 

 Large casts and one or two good specimens of Pecten turner i 

 Arnold, were collected from the roadside about one and one- 

 half miles west of Tomales. The Merced formation was not 

 recognized on the south side of Walker Creek along the 

 coast. Eastward from Tomales toward Petaluma, the road 

 leads through the village of Two Rock where the Franciscan 

 outcrops boldly. In most of the wells dug in the low, flat 

 plain, marine shells were encountered at a small depth. Near 

 the church in this town, on a slight elevation of about 30 

 feet above the plain around Two Rock, a yellow sandstone 

 entirely surrounded by Franciscan cherts yielded casts of 

 Leda, sp., and a few other indeterminate marine shells. Thus 

 we have evidence that the Merced was here laid down upon a 

 decidedly irregular surface. For two or three miles only, 

 Franciscan rocks outcrop along the road. As Petaluma is 

 approached the hills are capped by yellow and tan-colored 

 tuffaceous sandstones. In and around Petaluma good proof 



