326 CALIFORNIA ACADEMY OF SCIENCES. 



examined it will be noticed that quite a number of them 

 in the upper part of their course run nearly due east. It 

 will also be noticed that in many of these cases the rocks 

 exposed upon the two sides of the stream differ. This 

 has led to the suggestion that a system of east and west 

 faulting exists in the foothills, and that the streams have 

 followed these faults. 



All .through the region, but especially at the northern 

 end, are found small undrained basins, many of them 

 containing standing water all the year. Several of these 

 have been cut into in comparatively recent times by back- 

 ward cutting streams, and fault lines exposed. This is 

 very finely illustrated at the head of Wood's Gulch, where 

 the faulting appears to have produced such an undrained 

 basin, the fault scarp forming a perpendicular or over- 

 hanging cliff. Gradually the basin filled in against this 

 face, partly by washing from the surrounding hilltops, 

 partly by wind deposits, partly by fragments from the face 

 of the cliff, until all trace of the fault is covered up, only 

 to be exposed when erosion eats its way into the basin. 

 Judging from those we can examine, these little basins 

 are the result of faulting, and by an examination of the 

 map we can get some idea of the amount of faulting that 

 has taken place. 



It would thus seem, from what has been said, that the 

 structure which has resulted from the last uplift is essen- 

 tially fault structure, the area having been cut up with 

 fault lines which follow two main directions, and prob- 

 ably others which were not discovered. 



Correlation. — For convenience we may consider sep- 

 arately the area from Point Montara to Capitola, that 

 from Seven Mile-Beach to Milbrae, and that from Red- 

 wood City southward. 



The first division, from Point Montara to Capitola, has 

 yielded the following fauna : 



